188 



ZOOLOGY. 



18. Reproductive Organs. Thejemale is peculiar in 

 having only one ovary, apparently median, but really the 

 right, that of the left side disappearing during development. 

 The oviducts occupy a similar position to those of the frog, 



but owing to the absence 

 of lungs and forward 

 position of the heart, 

 their anterior ends (with 

 the internal openings) 

 come together in the 

 middle line between the 

 pericardium and the liver, 

 and there is a large 

 funnel - shaped united 

 opening. Each oviduct 

 is a nearly straight tube, 

 bearing an oviducal gland 

 a little way from the front 

 end, and opening pos- 

 teriorly into the cloaca. 

 The eggs are very large 

 about half an inch in 

 diameter when ripe 

 and only two are laid 

 at a time, one by each 

 oviduct. As they pass 

 through the oviducal 



, , /,, 



gland, an egg-case (ng. 

 100) is secreted around 

 them, the curled elastic 

 threads of which entangle 

 in sea-weed. In this 

 case the embryo safely 

 undergoes its develop- 

 ment. In respect of its reproduction the dogfish follows a 

 higher method than the frog making sure that the few 

 eggs laid will reach the adolescent state, instead of trusting 

 to the chance of a few being lucky out of many eggs badly 

 provided for. 



In the male we have a pair of large long testes, which are 



Fig. 



99. FEMALE REPRODUCTIVE ORGANS 

 OF DOGFISH. 



(Slightly diagrammatic.) 



