454 MK. J, n. LLOYD ON THE STRUCTURE AND LTFE-UISTORY 



mass of protoplasm, and acquire distinctness as they approach 

 the oviduct. 



The ova vniy in lengtli from 47-5 /x to 52 fi, and in breadtli 

 from 28-75 /x to 34-1 [x. Tlie thickness of the sliell varies from 

 6-25^ to 6-52 /A As a rale a coiled-up larva is formed within 

 the shell before the "eggs"' are extruded from the uterus. 



It is possible to burst the "eggs"' under a cover-glass and set 

 free the contained larvfe, which average 201 fx in length. They 

 are slightly attenuated towni'ds the head-end, which is charac- 

 terised by two protruding lips as in the adult, but there is no 

 cuticular collar. The tail ends in a point, and is bent at nn angle 

 to the remainder of the body, but exhibits no sexual differen- 

 tiation. 



Text-figure 3. 



Tail of matuve female Proleptns scilUcola. 



The male reproductive system is of the usual type. 



The excretory system consists of two canals, which pursue a 

 sinuous course, one in each lateral line. From each canal 

 a single branch descends to the ventral surface, where they unite 

 just before reaching the excretory pore. 



The nervous system consists of a well-defined circumceso- 

 phao'eal ring, which gives off numerous branches both anterioi'ly 

 and posteriorly. 



Life- History. 



The literature dealing with the life-history of Prolej)tus scilli- 

 cola is scanty. In 1865, Mcintosh (10) described "The Tre- 

 matode Larva and Ascaris of the Carcimis tncsnas." He 

 discovered two specimens of his so-called Ascaris, one of which 

 was lost, but his description of the other in some respects agrees 

 with that of Proleptits scilUcola. 



