and vascular or vaso-motor nerves, develops first. Schenck and Birdsall (Archives of Medicine, vol. I, No. 2), on the Embryogeny of the Sympathetic, consider this system as composed of masses originating in the central nervous system. This is a truth from one standpoint, and that a very narrow one. Blending the results of comparative embryology and anatomy, the sympathetic precedes the creation of other systems.

The second system to appear phylogenetically is the spinal, equivalent in the invertebrates to their "cerebral" ganglia.

The third system is the intervertebral, the swellings upon the posterior roots of the spinal nerves.

4. The cerebellum is formed from fused hypertrophied intervertebral ganglia.

Many sensory cranial nerves pass through this organ and by the fusion of these originally separate centres coördination occurs necessarily.

Excessive development on the one hand, or want of development on the other, places all the ganglionary tubercles and lobes of the encephalon in the third system category. Thus the præ-frontal lobe of the cerebrum, the occipital and temporal lobes, the olivary body, the olfactory lobe, the mammillary eminence, the epiphisis cerebri, the tubercula bigemina, the petrosal and Gasserian ganglia were originally intervertebral ganglia, and still maintain resemblance to these ganglia in many particulars.

5. The præ-frontal lobe is the last intervertebral ganglion to develop. It grows larger in the scale of intelligence and presses the occipital (see the brains of monotremes and marsupials) backward, downward and forward, thus forming the temporal (or what has been erroneously termed the middle) lobe.

6. The cerebro-spinal nerves, in some cases, preserve their original projections from and to muscles, but these nerves may also have not only a distribution to the viscera, as has the pneumogastric, but may also project into and from other system-centres. The lateral columns of the spinal cord, the tegmentum and crura cerebri in their main mass may thus be regarded as cerebro-spinal nerves of the highest series, having lower system-centres for peripheries. The præ-frontal lobes thus exert an inhibitory control over the highest centres, because such centres are peripheries for the nerves of these foremost ganglia.

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EVIDENCES OF THE EFFECT OF CHEMICO-PHYSICAL INFLUENCES IN THE EVOLUTION OF BRANCHIOPOD CRUSTACEANS. BY CARL F. GISSLER, of Brooklyn, N. Y.

DURING the winter months1 Eubranchipus vernalis Verrill 2 occurs near Maspeth, Long Island, in immense numbers in large communicating ponds containing clear, yellowish fresh water. In January last I found, in a small and entirely isolated pool, less than a hundred paces from the above mentioned place, a number of perfectly colorless, smaller, but sexually mature individuals of branchiopod Crustaceans. The bottom of the pool is a white and very soft clay and the water itself is of a milky color. I collected a number, and observed the following characters:

A. Very few individuals of both sexes bearing, with the exception of transparent body, and the red furca of the post-abdomen, the same characters as Eubranchipus.

B. A great number of colorless individuals from 15 to 22 mm. in length. These differ from the larger, red Eubranchipus in the following particulars: Cephalic scute large and convex. Basal joint of male clasper cylindrical. Claspers crossing each other, short, tip of second joint with a blunt, minute tooth. Second joint more or less conical, tapering. A number of full-grown forms between sets A and B occurred, evidently transitory stages. I expect soon to give an account in Dr. Packard's Monograph on Phyllopod Crustacea, of the sexual organs (to be illustrated by a plate), copulation and the biology of these colorless individuals. C. A single specimen of male Chirocephalus.5

D. A hermaphrodite. Sexual organs separate, both male and female claspers present.6

E. A single male individual with a minute tooth on the second joint of its right clasper, tooth wanting on the left. Left clasper in normal position, right clasper twisted around, thus apparently

1 From January till April.

2" Observations on Phyllopod Crustacea of the family of Branchipidæ with descrip tions of some new genera and species," by Prof. A. E. Verrill, 1869.

The normal red Eubranchipus has a white furca. Pale specimens of Streptocephalus Watsoni Pack. have also a red furca.

F. Spangenberg's paper in Zeitsch. f. wiss. Zool., XXV, Supplem, 1875, p. 14. Proved to be a very large specimen of Chirocephalus Holmani Ryder. March 22, 1881, I found a large pond between Glendale and Ridgewood, Long Island, densely populated with both Chirocephalus Holmani Ryder and Eubranchipus vernalis (normal). The former is described in Proceed. Acad. Nat. Sciences of Philad., 1879, p. 200. I described it in American Naturalist, February, 1881.

The claspers are the second pair of antennæ, transformed into auxiliary copu lation organs.

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8

preventing the animal from using it in copulation. The tooth is probably a substitute for the wrongly placed hook and assumes its function. This exemplifies Dr. Dohrn's theory of the consecutiveness of functions in one and the same organ, brought about by evolution. As to the latter I refer to papers by Prof. Edw. D. Cope in the American Naturalist: "The Laws of Organic Devel opment," 1871, and "A Review of the Modern Doctrine of Evolution," 1880. Dr. Moritz Wagner's migration theory 9 as well as Dr. Chas. Darwin's selection theory 10 may be employed to explain the occurrence of the above-mentioned sets, A, B, and probably C. First, I must mention that, on keeping a number of Eubranchipus, ♂ and (the latter with ovaries filled and oviducts empty) together with a number of sets A and B, ♂ and o̟ (9 in the same condition) during five days, I could never observe a single case of crossing: on the contrary the two (red and white) avoided each other, and only copulated among themselves. Now, as to set A, I consider them to be the first generation of Eubranchipus, brought along with mud into the little clay pool, by waterbirds from the neighboring larger ponds. (See Prof. J. A. Ryder's note in Am. Nat. XII, page 703). The transparency of their bodies was produced by the chemico-physical influence 12 of the little clay pool and not by "Mimicry." As the pool is an isolated one, there was no chance for the absorbing (or obliterating) influence of crossing with the original red Eubranchipus; consequently, the offspring of the new colorless race, influenced by different factors, was liable to submit to still further evolutionary transformations which I believe are realized in set B. The animal gradually degenerated into a much smaller one with the above-mentioned characters. The factor that produced it was a conservative one, favoring the preservation of this new species.13

8"Der Ursprung der Wirbelthiere und das Princip des Functionswechsels." Gene alogische Skizzen von Dr. A. Dohrn, 1875.

"Die Darwin'sche Theorie und das Migrationsgesetz der Organismen” von Dr. Moritz Wagner, 1868. The refutation of Wagner's law of migration was attempted by my former tutor, Professor Dr. Aug. Weismann (“ Ueber den Einfluss der Isolirung auf die Artbildung" 1872); owing to a misconception of Wagner's paper he combined his theory with Darwin's selection theory, whilst both theories considerably deviate from each other as regards the compelling mechanical cause. See also Kosmos, IV, April, 1880. Ueber die Entstehung der Arten durch Absonderung," von Moritz

Wagner.

10 On the Origin of Species by Means of Natural Selection," 1859.

11 F. Spangenberg in op. cit., pages 51 to 56.

12 W. J. Schmankewitsch in Zeitschr. fuer wiss. Zool., 1872, 1875 and 1877.

13 Professor Huxley's "The Crayfish:" In a strictly morphological sense, a species

is simply an assemblage of individuals which agree with one another and differ from

the rest of the living world in the sum of their morphological characters.”

1

The factor that produced the individual E was a compelling mechanical cause, originating in a pathological condition. According to Dr. Chas. Darwin the mechanical cause enters into activity with the appearance of "favorably varying" individuals whose morphological deviations are either inherited or adapted."

As to C, the genus Chirocephalus, I have reason to suspect in it the winter form of Streptocephalus. The successive appearance of Chirocephalus and Streptocephalus in one and the same pond near Woodbury, N. J. (Am. Nat. XII, 703, J. A. Ryder), rather strengthens my assumption.

The hermaphroditic form D shows characters closely relating it to set A. From the study of comparative anatomy it follows that Hermaphroditism, i. e., the coëxistence of both male and female sexual organs in one individual, is the primitive condition of sexual differentiation, which may in time be followed by a complete separation of the sexes. (See Dr. E. Haeckel's Anthropogenie, pp. 395, 681, etc). Hermaphroditism 14 and Parthenogenesis 15 can be regarded as cases of Atavism,—as a re-occurrence of former primitive conditions. Further progress in differentiation, of the sexual conditions Hæckel ascribes to division of labor (Arbeitstheilung). The bilateralism in this hermaphrodite indicates close relationship and coordination between the sexual organs and auxiliary copulation organs.

According to Dr. Chas. S. Minot's theory (Am. Nat., XIV, Febr. 1880), it is possible that a male genoblast was formed by the splitting of a neutral cell on one side, and a female genoblast in the same manner on the other side, of the post-abdomen at an early larval stage, and that then, as the animal became gradually more developed, the second pair of antennæ (not hitherto sexually distinguishable) transformed themselves symmetrically in accordance with the bilateral position of the genital glands and their exits. Unfortunately we are ignorant of the causes and conditions which impel an animal, when capable of producing genoblasts, to become either male, female or hermaphrodite.

14 Hermaphroditism in Crustaceans occurs normally in Cirripeds and parasitic Isopods. Exceptions are recorded (a) In the European lobster, by F. Nicholls, Phil. Trans. Royal Society, vol. 36, p. 250, 1730. (b) In free-living Isopods of the genera Cirolana and Conilera, by Paul Meyer, Mittheilungen aus der zoologischen Station zu Neapel. Taf. V: Ueber den Hermaphroditismus bei emigen Isopoden. pp. 165 to 179. 1878. (c) In certain water-fleas, Daphnia pulex, D. Schafferi, Alona quadrangularis, by Wilhelm Kurz, 49 Bd. Sitzungsberichte der k. Akademie der Wiss. I. Abtheilung. 1874: Ceber androgyne Missbildungen bei Cladoceren.

15 Co. sult I rof. Dr. C. T. v. Siebold's "Parthenogenese der Arthropoden," 1871.

ON COLOR-BLINDNESS. By B. JOY JEFFRIES, of Boston, Mass.

[ABSTRACT.]

DR. Jeffries first described the natural condition of the color sense, and illustrated some of its peculiarities as related to colorblindness. The complementary after-image of a color can be readily seen by gazing at the red setting sun, when, if we turn our eyes to the east, we shall see a green rising one. Looking steadily at a yellow spot on white, and turning away, we see a blue one, etc. After looking intently at a red or green light as used for instance on railroads and on vessels, one cannot help momentarily seeing the reverse color. The centre of the retina has the greatest power of form-perception; we must fix our eye steadily to see anything very distinctly. The same with color. All colors fade in intensity outward from the centre of the retina. In a central zone we can distinguish all three of the colors now considered primary, viz.: red, green and violet. In a zone outside of this our red perception fails, and in the outer portions still of the retina green fails, and we see blue or violet only. Now we have red, green and violet blindness, resembling, so to speak, the conditions of these zones. This must not, however, be too strictly construed. Color-blindness may be best described thus: Those who are red, or green (one involving the other), or violet blind see all objects having these colors as gray or grayish, in the proportion in which they are color-blind and the depth of the pigment. A color mixed with their faulty one will be, so to speak, muddy. Many thousands of examinations have. been made all over the world, with the same result as his He has tested 17,695 males, finding 739 color-blind in greater or lesser degree, viz., about 4 per cent. With females it is very rare, which, however, their familiarity with the colors does not account for. He tested 13,893 females, finding only ten colorblind. Age, race, color, education, condition of civilization, all seem to have no effect, as tests have been now made from the north pole to the equator, and throughout Europe and America. It is congenital, largely hereditary and handed down through the females, though they escape it. It may be artificially produced by putting a person in a cataleptic or hypnotic state; also those color-blind who can be put in this state are temporarily relieved of their defect. It is incurable by any known means. It may be caused by tobacco and alcohol poisoning, by injuries affecting the