EMBRYOLOGY OF CRYPTOBRANCHUS 83 



fall and winter, which suggests an autumnal fertilization, though 

 it is possible that spermatozoa are left over from a spring fertili- 

 zation. The method of transference of the seminal fluid from the 

 male to the seminal receptacle of the female is unknown. 



The breeding habits of some urodeles in which internal fertili- 

 zation takes place by means of spermatophores (e.g., Amblystoma 

 punctatum and Diemyctylus) have been considered by the writer 

 in former papers (Smith, '07, '10 and '11). FertiUzation is exter- 

 nal in the anura, internal in the apoda. 



In the elasmobranchs and holocephali, fertilization is internal. 

 In the crossopterygian Polypterus (Harrington, '99; Kerr, '07 b), 

 during the breeding season the anal fin of the male is modified in 

 such a manner as to suggest internal fertilization; or possibly it 

 serves to direct the sperm against the stream of eggs issuing from 

 the female. Nothing conclusive is known regarding the method 

 of fertilization in the dipnoi. In teleostean fishes, with a few 

 exceptions, fertilization is external; e.g., as in Chrosomus (Smith, 

 '08). 



The question whether external fertilization in Cryptobranchus 

 is primitive or secondarily acquired will be discussed under phylo- 

 genetic considerations in a later section. 



7. The brooding habit 



In a previous paper (Smith, '07) a paternal brooding habit was 

 described for Cryptobranchus. This was observed in aquaria, 

 and more extensively under natural conditions. 



The data on the existence of a paternal brooding habit under 

 natural conditions, while necessarily incomplete, are quite conclu- 

 sive. In one case, a male occupying a nest containing eggs was 

 observed to fight and drive away several males and a spent 

 female which were attempting to enter the nest (Smith, '07); 

 in another case, a male occupying a nest containing eggs was 

 observed to oppose the attempt of a single male to enter the nest. 

 It is not always possible to tell whether an adult is present in the 

 nest; the rock may be too large to overturn, and while the eggs 

 may be obtained by tilting the rock with a crow-bar, this method 



JOURNAL OF MORPHOLOGY, VOL. 23, NO. 1 



