GERM CELLS AND THEIR FORMATION 



105 



fertilization must be internal, and the sperm are then definitely intro- 

 duced into some reproductive cavity of the female. 



An interesting series of relations may be traced illustrating the grad- 

 ual increase in the certainty with which fertilization shall be accom- 



B 



FIG. 53. Forms of spermatophores. A, B, C. The Insects, Loricera, Locusta, 

 and an Ichneumonid. From Korschelt and Heider, after Gilson. D, E. The 

 Urodeles, Amblystoma and Diemyctylus. From Bertram Smith. X 3. F. Peri- 

 patus edwardsii (incompletely developed). After von Kennel (Korschelt and 

 Heider). 



plished, whether it be external or strictly internal. First, among many 

 of the Crustacea, Annulata, Gasteropods, Cephalopods, and Amphibia, 

 there is a process of pseudo-copulation or amplexus, where, sometimes 



