884 DR. F, E. BEDDARD ON 
parenchyma externally. These fibres, however, are not exactly 
like those which constitute the longitudinal muscular bundles. 
Although very wide when compared with the delicate fibrils that 
one expects to find in this situation, they are little if anything 
more than half the width of the longitudinal fibres. There is 
also a difference in the way in which they absorb the logwood 
stain, indicating a denser, because more deeply stained, outer 
layer. I do not attempt a further description of these fibres, as 
the material was not preserved in a way likely to bring out greater 
detail of structure. But enough is plainly visible to show that 
the dorso-ventral musculature in this worm is different from 
that usually met with in this situation among tapeworms. It is 
now necessary to point out that, in the younger proglottids, these 
thick dorso-ventral muscles are not visible. As the mode of pre- 
servation and staining has been identical, there can be no question 
here of a failure to detect the fibres in question, which I have 
looked for both in transverse and sagittal sections. Fine delicate 
fibrils can be seen, but nothing like the muscles just described, 
which are even: recognisable under quite low powers. It seems 
clear, therefore, that they appear; but whether they do so in the 
shape of new fibres or of a thickening of more slender fibres 
present in the younger proglottids, | am unable to say. But in 
any case there is a chan ge of structure in the medullary paren- 
ehyma as it grows older which is not a degeneration, and which 
appears, therefore, to be a preparation for some function, which is 
possibly that of a receptacle for the ripe embryos. It is for these 
reasons that I think myself justified in speaking of a paruterine 
organ in Ofiditenia which is, however, of a most generalised 
kind. 
The above description amounts in reality chiefly to an 
emphasised re-assertion of the facts concerning the medullary 
parenchyma of Otiditenia, already dealt with in my paper on 
that genus. The facts lead me to the inference that we have in 
this tapeworm the commencement of the formation of the 
paruterine organ, which is more differentiated in other genera of 
Davaineide, as well as in the Paruterine among the Hymeno- 
lepidide. The paruterine organ of Stilesia, and that of its 
immediate ally Avitellina, seems to me to be a different structure 
altogether, though serving much the same function. In Oétidi- 
tenia, then, there is an alteration of structure in the whole 
medullary layer in the direction of increased firmness; but there 
is no special part of that parenchyma set apart for the shelteri ing 
of the growing embryos. In a sense, therefore, I was right in 
not describing the existence of a paruteri ine organ ; but. with 
equal truth it may be said that this genus has the equivalent of 
a paruterine organ. In this genus we see the next stage to that 
exhibited by many genera in which the ripe embryos lie in the 
unaltered parenchyma, such as Oochoristica, Linstowia, ete. A. 
slight increase of specialisation of the conditions observable in 
Otiditenia leads us at once to such a form as Sphyroncotenia, 
