184 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



refracting corpuscles are scattered through the substance of 

 the body (Fig. 48, A). It is probable that these are more or 

 less calcified connective-tissue corpuscles. Similar bodies 

 which occur in some Trematoda were found by Claparede to 

 be lodged in dilated ends of the water-vessels, but it would 

 appear that they are not so situated in the Cestoidea/ 



The distance between these transverse grooves, and their 

 depth, increase tow^^rd the hinder end of the body ; and each 

 segment is eventually found to contain a set of male and 

 female organs. The genital organs are constructed upon the 

 same general plan as those of the Trematoda^ but the uterus, 

 as it fills with ova, usually takes the form of a ramified sac. 

 At the extreme end of the body, the segments become de- 

 tached, and may for some time retain an independent vitality. 

 In this condition each segment is termed a proglottis y and 

 its uterus is full of ova. 



The embryo is developed in these ova in the same way as 

 in the Tremcitoda ; and, as in the latter group, it may either 

 be ciliated (as in Bothriocephalus) or non-ciliated, which last 

 is the more usual case. The embryo is a solid morula, on one 

 face of which four or six chitinous hooks, disposed symmet- 

 rically on either side of a median line, are developed. 



Fig. 47.— "Oiaarams illustrative of the relation between T/rnia, CijsUcercus, Coennrus, 

 and EcldiwcoccuR.—A, B, youn? Tcznm in the Scolex staae. ttie latter with an 

 en\?i\-^('drec(>pfacultim ScoUcAs, into v;\\\q.\\ the head and neck are withdrawnin 

 C, Ci/f^fic.^rcr/!^ ,• D, C'e7iurns : E. hypothotiral condition of KcMjiococcks, in which 

 "• Tfpnia heads" are developed only on the inner surface of the primary cysts; F, 

 Echinococcus with secondary cysts; G, embryo Taenia (after Stein). 



If the eg^ is placed in appropriate conditions, the hooked 

 embryo emerges from the shell, and rapidly increases in size. 



1 Sommer and Landois, " ITeher den Bau der creschlcchtsrelfen Glieder 

 von Bothrioc^.pkalus Intti.t.''^ {Zeitschrift fi'ir wiss. Znoloaie^ 1872). Leuckart, 

 however, maintains the contrary opinion, "Die meuscliliclien Parasitcn," p. 

 175. 



