712 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 



the external genital apertures and the cirrhus-pouch can be distinctly 

 seen. All the efferent ducts extend at first in a straight direction back- 

 wards to near the posterior margin of the joint, where the rudiment of 

 the shell-gland and ovary can be distinguished between them. Both 

 originate as appendages and processes of the streak-like rudiment, 

 the shell-gland at the posterior end, the ovary at a short distance in 

 front of it, extending on either side like a pair of wings. At the same 

 time the testicular vesicles become visible in the median region of the 

 joint. They occupy for the most part the anterior clear portion of 

 the joints, while the yolk-glands, at first small and clear, are to be 

 detected somewhat farther back in the lateral areas. 



FIG. 372. Development of the reproductive organs in Botkrio- 

 ccphalus latus. ( x 25.) 



When the various organs have thus been mapped out, they rapidly 

 acquire their full development. Even at a distance of 60 cm. from 

 the head, the uterus, formerly but slightly looped, has, though still 

 empty, acquired essentially its final shape, except that the limbs of 

 the loops are shorter and more distinct than subsequently. Shortly 

 afterwards copulation seems to occur, for a few centimetres farther 

 back a grumous mass, penetrated by spermatozoa and balls of shell- 

 substance, is found in the posterior end of the uterus, and beside this 

 appear the first hard-shelled ova, clear and few in number. For a 

 time the ova lie in a single discontinuous row, but become by further 

 pressure more and more closely aggregated. The width of the uterine 

 canal increases, the limbs of the several loops become approximated, 

 and the appearance previously described is soon exhibited. The more 

 the eggs accumulate the darker becomes the colour of the uterus, and 

 the more distinct its definition. In older joints it appears through 

 the cortical layer as an almost blue, leaf-like lobed mass. 



