454 MR. J. IT. LLOYD ON THE STRUCTURE AND LIFE-IIISTORY 



mass of protoplasm, and acquire distinctness as they approach 

 the oviduct. 



The ova vary in length from 47*5 /x to 52 /x, and in breadth 

 from 28*75 /x to 34'1 fx. Tiie tiiickness of the shell varies from 

 6'25 fj. to 6*52 //- As a rule 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 larvae, which average 201 /x in length. They 

 are slightly attenuated towards the head-end, which is charac: 

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

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

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

 tiation. 



Text-figure 3. 



Tail of mature female Troleptns sciWcola. 



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 circumoeso- 

 phageal ring, which gives off' numerous l)ranches both anterioi-ly 

 and posteriorly. 



Life- History. 



The literature dealing with the life-history of Proleptus scilli- 

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

 matode Larva and Ascarls of the Carcimis mcenas." 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 P^^oleptus scillicola. 



