CHAPTER XXV. 



EMJBRYOLOG1CAL METHODS.* 



585. Artificial Fecundation. This practice, which affords 

 the readiest means of obtaining the early stages of develop- 

 ment of many animals, may be very easily carried out in the 

 case of the Amphibia an lira, Teleostea, Cyclostomata, Echino- 

 derrnata, and many Vermes and Coelenterata. 



In the case of the Amphibia, both the female and the 

 male should be laid open, and the ova should be extracted 

 from the uterus and placed in a watch-glass or dissecting 

 dish, and treated with water in which the testes, or, better, 

 the vasa differentia, of the male have been teased. 



Females of Teleostea are easily spawned by manipulating 

 the belly with a gentle pressure ; and the milt may be 

 obtained from the males in the same way. (It may occa- 

 sionally be necessary, as in the case of the Stickleback, to 

 kill the male, and dissect out the testes and tease them.) 

 The spermatozoa of fish, especially those of the Salmonidse, 

 lose their vitality very rapidly in water; it is, therefore, 

 advisable to add the milt immediately to the spawned ova, 

 then add a little water, and after a few minutes put the 

 whole into a suitable hatching apparatus with running 

 water. 



Artificial fecundation of Invertebrates is easily performed 

 in a similar way. For methods of artificial Parthenogenesis 

 see HARVEY, Biol. Bull. Wood's Hole, 1910, p. 269. 



* The sections in this chapter treating of Mammalia, Aves, and Pisces, 

 closely follow the Traite des Methodes Techniques, LEE et HENNEGUY, 

 and are due almost entirely to HENNEGUY. The corresponding parts 

 of the Grundziige, LEE and MAYER, are taken from this work, and there- 

 fore also due to HENNEGUY, which I regret to observe has not always 

 been understood, though duly pointed out in the Preface to the first 

 edition of the Grundziige. 



