1911] 



Smith, Natural History of Amiy stoma. 



21 



HISTORY OF THE EGGS BEFORE HATCHING. 



During the early stages of development the space filled with 

 liquid surrounding the individual egg is small, but in the later 

 stages it enlarges to keep pace with the growth of the embryo. 



I have searched in vain for spermatozoa imbedded in the egg 

 envelopes of A. jeffersonianum and A. punctatum. . Clarke ('79) 

 says of A. punctatum breeding in captivity: "The eggs were 

 found to have adhering to their outer shells a considerable num- 

 ber of these male elements, but I could not find, after trying a 

 great many times, any spermatozoa within even the outer shell." 

 So far as this evidence goes, it would seem that in the process of 

 internal fertilization the spermatozoa ascend the oviducts and 

 reach the eggs before the envelopes are laid down. But Kings- 

 bury ('95, p. 290) says: "I have never seen zoosperms in the 

 oviducts of any species sectioned by me, in almost all of which 

 the lower portion of the oviduct was examined." In Crypto- 

 branchus, in which fertilization is external, spermatozoa are 

 always to be found imbedded in the egg capsule and floating in 

 the fluid-filled space within. 



I have found polyspermy occurring in the eggs of A. tigrinum. 

 This point will be discussed in a later paper. I have not yet 

 studied the fertilization stages of the other species. 



The low vitality in the eggs of A. jeffersonianum reported by 

 Piersol ('10). resulting in the loss of about three-fourths of the 

 eggs before gastrulation, has not been evident in the material 

 studied by me. 



The approximate time record, not quite complete, for the two 

 species, follows: ^_ 



