SIPUXCTLOIDEA. 



However, it is clear that in this case, at any rate, the introvert is relatively much 

 longer than in the cases originally described. I turn, however, to a second of the 

 specimens lent me, which I have cut open, and find that the unextended introvert 

 which lies inside the body is now markedly less than half the body length. Now it 

 seems not at all unlikely, on a priori grounds (I have no actual observations to offer in 

 this case), that the introvert, when pushed in amongst the organs of the body, should 

 contract to a considerable extent, so as to occupy as little room as possible ; and that, 

 therefore, the normal length (if one can speak of any such thing) in this case may be 

 considered as being about half the body length. But over and above this, we find 

 that the number of gut-coils in this specimen is something between 30-40, while 

 capsiforme is said to have only about 20. Since, however, I have been kindly 

 permitted to examine these specimens pretty closely (I have not been able to open the 

 other two), I am able to state that I see no reason to doubt the accuracy of their 

 identification with capsiforme, despite these differences. That is to say that I, 

 assuming a much more careful examination on the part of the original identifier, am 

 not willing to controvert his decision, and that my own observations tend to support 

 it. And so I provisionally assume that considerable differences of this nature may be 

 expected to occur, at auy rate within the margaritaceum group. 



Pit. papillosum, Ph. capense, and Pit. hanseni appear to be sufficiently distinct 

 from the mannu-it<n:< ><///. group to render any detailed comparison with this species 

 unnecessary. On the whole then, it seems reasonable enough to consider this form as 

 a type differing from Ph. margaritaceum and Ph. capsiforme ; and for much the same 

 reasons that we can so separate P/t. antarcticum and Ph. fuscum. But the comparison 

 with the two latter forms is a much more difficult matter. In the first place, much the 

 most striking feature in the majority of these specimens, as viewed with the naked eye 

 or the lens, is (a) the thinness and semi-transparency of the skin, and (b) its extreme 

 smoothness, the papillae only being barely visible with the aid of the lens (they are all 

 small specimens) on the hind end, or sometimes also at the base of the introvert. 



In these features of their general appearance, in their light, somewhat straw-like 

 colouration, coupled with the abruptly pointed termination of the body, and the 

 localisation of the papillae, they recall the general facies of Ph. vulffare more than that 

 of any other species with which I am familiar. And it is in just these features that 

 they seem to differ so markedly from Ph. untarctieum and Ph. fuscum, in which the 

 body-wall is relatively thick, the colour is dark, and a system of cross-striation is 

 present at the hind and front ends of the body, which appears to be at best but weakly 

 represented in this form. "NVo may then proceed on the conceivable presumption that 

 these are a single (i.e. from the specific point of view mouovalent) group of points ; in 

 other words, that we are dealing with one specific point only, and that that point may 

 be either variable according to size and age, or variable within the species. Passing 

 on then to other points, we find a clear resemblance to Ph. fu*cum in the close 

 approximation of the openings of the segmental organs to the line of the anus. 



Y 2 



