MAMMALIAN CESTODES. 565 



and are developed in the posterior region of the proglottid 

 only, but all the same occupy the greater part of such proglottids. 

 There is no regulaiity in the dispersal of these cavities, so far as 

 I have been able to make out. They lie here and there, and are 

 never crowded like the testes ; among them lie the remains of the 

 testes in the most posterior segments, where the testes are most 

 fully reduced. The cavities increase in size 7J«?'^ |9rtss^t with the 

 development of the embryos contained within them. In the more 

 anterior part of the body the spaces are small and contain but a 

 single egg or embryo just commencing to divide, which does not 

 nearly fill the cavity. 



Text-fiy. 93. 



Diplopijlidium genettce. 



A portion of a nearly ripe proglottid showing ova (<?.) Ij'ing- in spaces in 

 the medulla. 



In the centre of the field is one ovum which has no cavity round it. 



Further back the cavities are lai-ger to accommodate the large 

 embryo with its wide egg-shell. Nowhere is there anything of 

 the nature of a lining membrane to these cavities. No nuclei 

 are distinguishable as forming a layer immediately suri'ounding 

 them, though the nuclei of the medullary parenchyma are, of 

 course, to be found frequently in the neighbourhood of the 

 limiting layer of the cavities ; but in these cases there is no 



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