48 



HIGH SCHOOL ZOOLOGY. 



they have been laid and have begun to develop into the young 

 fry, are carefully guai-ded by the male, who keeps them together 

 and swims over them, returning pertinaciously even after he 

 has been pushed away. A tropical form, the large eggs of 

 which are hatched in the mouth-cavity, and a Southern species 

 allied to our catfish, have been observed to take the fry into the 

 mouth, and allow them afterwards to escape. 



Fig. 19. — Diagram of several stages in Development of Catfish. 

 (Modified from Ryder). 



1, ovarian egg ; 2, egg in which fonnative yoke has separated to iip]>er pole ; 3, em- 

 bryo of second day ; 4, section through such an embryo, showinj,'- epiblast with nervous 

 system above, hypoblast below, and between them the mesoblast and the notochord ; 

 fi pnibryo of sixth day. 



