TAPE-WORMS OF THE SUB-FAMILY AVITELLININ^. 377 



The lamellae are at first composed of a mass of plasma 

 belonging to several nuclei and are fairly thick ; with further 

 development the thickness of the lamellae becomes less and 

 less, and they finally resenjble thin fibrillte on section. There 

 can, however, be no doubt that the structure is lamellar and 

 not fibrillar, as in whatever direction a section may pass 

 through a paruterine organ, one alwa3^s sees a concentric 

 arrangement of "fibres" running within the plane of the 

 section, but never by any chance sections through fibrillas. 

 As the lamellae grow older the nuclei atrophv and finally 

 disappear. 



Directly anterior to the uteri lie pads of fibrous tissue 

 (fig. 52), whose probable function is to give support to the 

 paruterine organ, and perhaps also to act as cushions between 

 the uteri and paruterine organs of adjacent segments. These 

 pads take their origin from myoblasts, which are very frequent 

 close in front of the uteri when the eggs arebegining to enter 

 that organ. The fibrous tissue, when fully developed, contains 

 scattered nuclei, and its fibrillar structure is fa'vly apparent. 

 It stains fairly vividly with eosin (fig. 48). 



The cirrus and cirrus pouch arise out of a common aulnge 

 with the vagina, as already explained above. The dense 

 mass of dark-staining nuclei, which gives rise to both, first 

 splits into two masses; these become surrounded by myoblasts 

 (fig. 44) ; then, in the middle of one of the two masses the 

 vagina begins to develop, the cirrus and part of the vas 

 deferens in the other. The epithelial cord arising in the 

 middle of the cirrus pouch anlage is at a very early stage 

 already convoluted, probably giving rise to the tvnsted portion 

 of the vas deferens enclosed in the cirrus pouch 



The vas deferens is, like the female ducts, formed of a solid 

 cord of epithelial cells surrounded by a basal membrane 

 (fig. 46) ; the hollow arises later. As in the female ducts, the 

 epithelium finally atrophies entirely. Its lumen is then 

 clothed with cilite. 



The cirrus is straight, 34 fx long by 3 fx in diameter ; it is 

 devoid of hooks, bristles or cilia of any kind ; it opens 



