1 1 





. ulicn- the mem th couple does not yet show the contorted form which 



it wil] probably present later. The difference in the form of the filaments may be >, 1 1 j > ] > 

 t<> indicate an alternation ol sterile and fertile mesenteries. 



In the lai there were twenty marginal tentacles, that is to say, a median 



tentacle and on the right side ten and on the lefl nine additional om-s, the must dorsal tentacle 



markedly smaller than the others. < >f labial tentacles there were seventeen, 

 nine to the right of the median line and eight to the left of it. As in the earlier stage there 

 no median labial tentacle, but the most ventral couple now corresponded to the first couple 

 n\ marginals, s<> that the tentacle formula was 



i ' -T 1 . T.M. T' + T 10 

 t s — t 1 . t 1 — t 9 . 



1 impared with the younger examples the most striking difference is this appearance of 

 the hrst couple of labial tentacles. They are considerably smaller than the second couple and 

 it would seem that their development is practically identical with that of the eighth labial and 

 ninth marginal couples. 



As regards the mesenteries, these have increased t<> twenty-three, twelve of which be- 

 long to the right side and eleven to the left. They present essentially the same structure and 



arrangement as in the younger examples, except that the 

 fourth couple of protocnemes, the acontiferous couple, are now 

 decidedly longer than the second couple (Text-fig. XIV 



The differentiation of the ectoderm of the tentacles 



into four hands is fairly distinct, but it is not carried to the 



extenl of giving the tentacles a quadrangular section, the 



condition they present being somewhat like that described by 



van Beneden for D. e/egans, although the histological details 



are quite different. On the lateral surfaces the supporting cells 



are closely packed, gland cells being rare and nematocysts, 



though present, relatively few. As a result the nuclei are closely 



packed and in sections stained with haematoxylin these regions 



are of a deep blue colour, contrast arly with the oral 



and aboral surfaces which are much paler in colour. This is 



due to the fact that on the aboral surface the nematocysts are 



verj abundant, and on both surfaces there are numerous large 



unstained gland cells, so that the supporting cells are much 



numerous and their nuclei somewhat sparsel) scattered. 



It is highly probable that this form is different from any of those described by van 



The individuals of /). armata and D. digitata which he described an- of about 



;am< ven slightly younger than the younger examples of D. malayensis, and yel 



■'.'. less disparity in the lengths of the protocnemes and deuterocnemes, and in both 



•'.i couple of protocnemes surpasses in length the second couple. And, as a further 



M 



XIV. 

 howing the arrangement of the 



and tentacles in nn older larva 

 nsis. 



