REVIEW. 



631 



granules in the (glandular) ectoderm-cells differ from these only 

 in being of smaller size. I have been very slowly and gradually 

 led to the conclusion that the bodies in question, which I propose 

 to call '^Metschnikoff cells/' are metamorphosed collar-cells; that 

 by their reaching to the exterior and becoming perforated, pores 

 are formed; and that the granules of these and of the ectoderm, 

 and of the glandular ectoderm in general (and possibly the 

 granular cells so frequently described beneath it in Si lice a), 

 are excretory. 



In the nucleus of the ovum Dendy finds in L. pelliculata 

 nucleoli and circumferential granules; in L. depressa, in 

 addition, a faint reticulum. In Asc. clathrus (nitric acid 

 and borax carmine) I find a distinct and typical reticulum 

 with small granules at the nodes. I have found also a large 

 nucleolus with vacuoles, possibly artificial. In the matrix 

 capsule of sponge embryos Dendy has almost established a pro- 

 prietary interest; in Leucosolenia Wilsoni he finds they 

 have no connection with ectodermal cells. In A. clathrus 

 ova occur which appear to have such a connection, but when full 

 of yolk they lie in sacs dependent in the gastral cavity, clothed 

 with collared cells, of which some are always metamorphosed, 

 and which are in continuity by the neck of the sac with the 

 general endoderm. It may be worth adding to his instances of 

 specially robust external spicules, besides Asc. cerebrum, 

 whose "tripods" are confined to the outer surface, Ascandra 

 r e t i c u 1 u m, in some varieties of which the acerate {" orceote ") 

 spicules are so confined, while in others they disappear. The rod- 

 like bodies he describes on the gastral surface of Sollas's mem- 

 brane inL. tripod if era I do not believe to belong to the sponge; 

 he himself accepts them doubtfully. But it is curious that 

 in the allied A. cerebrum and the variety of A. primordialis 

 which simulates its form (variety of A. cerebrum simulating 

 the spicules of A. primordialis? nova species ?) the collars and 

 flagella most frequently appear to be replaced by a network of 

 threads. Nothing but its " constancy and peculiar and regular 

 arrangement," to quote Dendy's words, could, however, give any 

 doubt that these are vegetable, which on the whole is at present 



