THE MICROSCOPE. 



Vol. V. ANN ARBOR, MARCH, 1885. No. 3. 



RESULTS OF MICROSCOPICAL RESEARCH. 



f?YES in Chitons. — Among the Molusca is a curious group 

 J known as chitons. They are flattened and oval, and their 

 dorsal surface is covered with eight shelly plates, arranged one 

 after another in a longitudinal series. In every text book the 

 chitons are said to be blind. Professor Moseley showed last 

 August that this was a mistake, and now we have (Q. J. M. S., 

 xxv., p. 37) his complete paper, illustrated by three double 

 plates. In all genera the dorsal plates are covered with pores of 

 two sizes, and in many forms there are, besides, eyes provided 

 with cornea, lens, iris, and retina, composed of rods and cones ; 

 the relations of the retina to the nervous supply being much the 

 same as in most Mollusca, and entirely different from that in 

 Onchidium and the vertebrates. The pores are filled by sense 

 organs, and Professor Moseley, with reason, regards the eyes as 

 modifications of these. The eyes are exceedingly numerous in 

 some forms, and the author estimates that in Corephium there 

 are between 11,000 and 12,000 eyes in good condition. Profes- 

 sor Moseley gives an account of the distribution df the eyes 

 and pores in various species, and suggests that they may afford 

 good systematic characters. 



Some Points in Fish Embkyology. — From having been a 

 sadly neglected field, the study of the development of fishes 

 has recently acquired great prominence, but so greatly modified 

 are the teleosts, and so widely removed from the main verte- 

 brate stem, the interpretation of the facts they present is a mat 

 ter of no little difficulty. Several years ago Kupffer, a German 

 naturalist, described in the embryo of a fish, a peculiar vesicle 

 the relationships and homologies of which were far from ob- 

 vious. This has since been called Kiipffer's vesicle. Mr. J. T. 

 Cunningham (Q. J. M. S., p. 1, 1885) has essayed to solve the 



