84 GEiTERATrVE OKGANS. 



There were also a number of larger spherical cells, 

 from "OOOo" to "OOl" in diameter, and transparent, or 

 containing only a few granules. These may, perhaps, 

 be compared with the similar bodies found in the testis 

 of Oniscus. The walls of the triangular reservoir are 

 rather thick, and consist of nucleated cells. It contains 

 the spermatozoa and the bright, greenish bodies, as 

 well as some other globules, which resemble oil 

 globules. 



The walls of the accessory glands are also composed 

 of thick cells. They are completely filled by the 

 minute granules, which form an opaque mass. The 

 ductus ejaculatorius has an apparently chitinous 

 lining, which is strengthened, like the trachea and 

 some other chitinous parts in Articulata, by transverse 

 ribs, which, however, in this case are very delicate. 



I have never found any eggs of Oollembola suffi- 

 ciently transparent to permit a satisfactory observation 

 of the embryonic changes. Mr. Packard, however, 

 has recently given us the following account of the 

 embryology of Isotoma : 



" The eggs of Isotoma WalJcerU were found by Mr. 

 C. A. Walker, at Chelsea, under the bark of an apple 

 tree, on the 25th of April, 1870. They were either 

 laid singly or in small scattered groups on the damp 

 under surface of the bark. The eggs are spherical, 

 glistening white, with the chorion very transparent. 

 They measure '0625 of an inch in diameter. At the 

 date above mentioned many of the embryos had 

 hatched, as the young were found in various stages of 

 growth. They continued to hatch until May 6th. 



" Numerous eggs were observed in which the blasto- 

 derm had not yet been formed. In these, amid a mass 

 of minute granules, floated from two to four large oil 

 globules (PI. Ill, fig. 2 c), the largest of which was one 

 fourth the diameter of the egg itself, while there were 

 numerous smaller globules measuring about one fourth 

 the diameter of the largest cells. 



" The earliest stage I was able to observe (PL III, 



