The Histogenesis of Cysticercus pisiformis. 189 



to the thickness of the bladder wall, the increase of nuclei in the 

 latter and the grouping- of cells at one end of the larva, representing 

 the rudiment of the future head piece. In Fig. 15, a small part of 

 this rudiment is represented on a larger scale and in Fig. 16 a part 

 of the bladder wall of the same larva. The nuclei are closely 

 grouped in a S3'ncytium of parenchyma strands, whose general 

 alignment is perpendicular to the bladder wall. The structure of 

 the parenchyma and its nuclei is essentially the same as in the 

 preceding stage. There is a very rapid nuclear multiplication taking 

 place especially in the head piece rudiment and a great variation 

 in size of nuclei is apparent. The granular protoplasm, noted in 

 the preceding stage as distributed along the strands of the paren- 

 chyma network, is increasing in amount and gathering itself into 

 small irregular masses at scattered intervals {mcy, Figs. 15, 16). The 

 formation of a cuticula is not yet apparent altho the fibres of the 

 outer wall appear to be scaling oif, which process continues to occur 

 during cuticular development as will be noted later. The outer 

 wall of the larva is differentiated from the underlying parenchyma 

 by the arrangement of its fibres in two sheets which pass at right 

 angles to each other, the rudiments of the sub-cuticular muscle 

 layers (otn and im. Fig. 15). While the anterior end of the larva 

 assumes the histological structure of the adult tapeworm, the bladder 

 wall retains its embryonic character, with increasingly less differen- 

 tiation toward the posterior, and this is true even in old larvae. 



It will aid the reader to appreciate the development of the 

 tissues if he bear in mind thruout the words of Moniez (1881: 212): 

 "Nous pouvons nous expliquer maintenant l'origine et la structure 

 des appareils plongés au sein de ce tissu homogène. Nous croyons 

 qu'ils naissent tous aux dépens des cellules (du tissu 

 conjonctif) dont nous venons de parler." 



b) Parenchyma and Chalk Bodies. 



The development of the parenchyma beyond the earlier stages 

 presents nothing of striking interest. The fibres become more dense 

 and assume sharper outlines by loss of the granular protoplasm 

 adherent to them in the earlier stages, which is gradually consumed 

 in the manufacture of new tissues. Thus is established a firm, 

 elastic, supporting framework for the body, which interweaves itself 

 among the other tissues in the most intimate manner and forms, as 

 will be seen later, the groundwork of the cuticula itself. 



