February 18, 1898.] 



SCIENCE. 



227 



trasting background. The cover glasses 

 were mounted on the glass strips and held 

 in position by collodion. 



For the older stages, where the mem- 

 branes stretch far around the yolk, thick 

 (6 per cent.) collodion was moulded in 

 Eeighard's watch glasses, hardened in 

 chloroform and coated with black collo- 

 dion. The membranes were then iloated 

 over the mass, fixed in position with thin 

 collodion, and these mounted specimens 

 without membranes were fastened in posi- 

 tion on the glass slides with collodion. 



A separate series was made to show the 

 change of form of the brain in course of 

 development. 



On the AmblyopsidcB. C. H. Eigenmann. 



The members of the Amblyopsidfe and 

 their distribution are as follows : CJiologaster 

 cornutus, abundant in the lowland swamps of 

 "Virginia and Georgia ; Chologaster Agassizii, 

 subterranean streams of Tennessee and 

 Kentucky ; Chologaster papilliferus, springs 

 of Union and Jackson counties, 111. ; Amhly- 

 opds spelcBiis, subterranean streams of the 

 Ohio Valley ; Typhliehthys subterraneus, sub- 

 terranean streams of the Ohio Valley, 

 chiefly south of the Ohio Eiver ; Typhlieh- 

 thys rosce, subterranean streams west of the 

 Mississippi. 



The eyes of all the species except those 

 of Ch. Agassizii have been examined. In 

 Chologaster the eyes are normally placed 

 and functional. Ch. papilliferus possesses 

 the better eyes, but even here many signs of 

 degeneration are apparent, the inner layers 

 of the retina being less in thickness than 

 the pigmented layer. In Ch. cornutus the 

 pigmented layer forms two-thirds of the 

 thickness of the retina, the nuclear layers 

 are each composed of a single series of 

 nuclei and the ganglionic layer of cells 

 widely separated from each other. The lens 

 and vitreal body are normal. In all the 

 species examined the eyes have sunk be- 



neath the surface, the lens and vitreal body 

 have practically disappeared ; the eye has, 

 as a consequence, collapsed and is minute. 

 Part of the ganglionic layer forms a central 

 core of cells in Amblyopsis and T. subterra- 

 neus. In the former the pigmented layer is 

 highly developed ; in the latter, while still 

 present, it is entirely without pigment. In 

 T. roscB the eye has degenerated further 

 than in the eastern species. The central 

 core of ganglionic cells has disappeared; the 

 pigmented layer is imperfect ; the inner re- 

 ticular layer occupies a central, or rather 

 posterior, position around which the nuclear 

 layers are placed. Lens and iris are gone, 

 and the entire eye is but 40-50 a in di- 

 ameter. 



Conclusions : The three species of blind 

 fish are of independent origin. The results 

 of degeneration are not the same on the 

 homologous structure of the eye in the three 

 species. The degeneration is not the result 

 of arrested development or of ontogenic de- 

 generation. The eye of the Amblyopsidse, 

 reaching its greatest point of degeneration 

 in T. roscE, is the result of phyletic degener- 

 ation begun before the fish entered the 

 caves. Their degenerate eyes are not pri- 

 marily due to their habitat in caves, i. e., 

 to the absence of light; rather are they 

 found in the caves because they were largely 

 able to do without the use of their eyes, and 

 therefore succeeded in establishing them- 

 selves in the caves. In this they were aided 

 by their peculiar method of raising their 

 young in their gill cavities. 



Tlie two Common New England Salamanders, 

 Desmognathus and Spelerpes, and their Im- 

 portance as Laboratory Animals. H. H. 

 "Wilder. (Kead by title only.) 



Accessory Optic Vesicles in the Chick Embryo. 



W. A. Loot. 



It was shown that in chick embryos two 

 distinct sets of vesicles make their appear- 



