180 DR. F. E. BEDDARD ON THE 



In the posterior and riper proglottids the muscular layers of 

 the body differ from the same layers in the more anterior pro- 

 glottids ; and what is highly interesting to observe is the fact 

 that the alterations in structure do not appear to be due to mere 

 turgescence caused by the accumulation of ova in the uterus, but 

 are a distinct modification associated with a ripe proglottid. 

 The state of affairs in these proglottids is indeed comparable 

 with the modification of generative segments in certain Annelids. 

 One may frequently observe a degeneration of the muscular layers 

 in ripe proglottids of tapeworms which seems to be a matter 

 of pressure ; but the anatomical features met with in Amabilia 

 seem to me to belong to a different category. In transverse 

 sections through such proglottids, it is to be noted that, though 

 the uterus is well developed, it is not so huge as to occupy more 

 space than is available in immature proglottids further forwards in 

 the body. The network of tubes which constitute this organ are, 

 in all the proglottids that I have studied, of quite small calibre, 

 and though in places full of ova, are not over full, and indeed 

 here and there empty ; moreover, the eggs are not f ally developed : 

 the shell has not yet been formed. There is thus no tension 

 at all, and no mechanical explanation to be advanced. 



Moreover, the relative thickness of the medullary and cortical 

 layers is not altered, as it would have to be under such circum- 

 stances. Instead of the cortical layer being thinned by expansive 

 pressure from the medullary layer within, it is in places actually 

 thicker in proportion, as may be seen by a comparison of text- 

 figs. 3 & 4. It has in fact undergone an alteration which is quite 

 the reverse of degeneration, though accompanied here and there 

 by a disappearance of the bundles of longitudinal fibres, which 

 may of course, in a sense, be termed degeneration. In addition 

 to tracts from which the longitudinal muscle-bundles have dis- 

 appeared, but — be it observed — without any thinning of the 

 cortical layer as a whole, there are tracts where the cortical layer 

 has undergone a remarkable reduction, and this reduction occurs 

 rather suddenly as is shown in the accompanying figure (text- 

 fig. 4). 



Near the letter u l" in the figure the cortical layer is quite 

 normal ; the subcuticular layer, the bundles of longitudinal 

 muscles, and the transverse muscular layer are all obvious and 

 duly lettered in the figure. At a certain point there is a more 

 or less sudden alteration in the cortical layer. The dorsoventral 

 diameter is reduced to not more than one-quarter of its original 

 diameter. The longitudinal muscles disappear a little before 

 the cortical layer is more abruptly reduced, and at or about 

 the same place the transverse muscular layer becomes slightly 

 expanded and vanishes. The cortical layer is thus reduced to the 

 subcuticular layer only. Later on, this layer itself apparently 

 vanishes and the medullary layer appears to form the exterior 

 of the body. I find, however, that the cortical layer is really 



