1869.] and Membranipora Bengalensis, 48 



k. On the internal side of the larynx, and next to the entrance of 

 the stomach, are suspended the mesenterial-threads, or craspeda. 

 These are, in the present species, flat bands of one, or one and a half 

 inch in length, being of a pale greyish yellow colour, and with the 

 lateral margins partially rolled in, so as to have the appear- 

 ance of nearly cylindrical tubes. They hang down loosely, and the 

 greater portion of them lies in small heaps round the centre of the 

 base. Their more central position as regards the reproductive organs, 

 is clearly visible in the view of the base, (pi. X, fig. 5). There are 

 always numerous threads together, but they cannot be easily distin- 

 guished through the integument of the base. 



In figure 1, pi. XI, is given a representation of a specimen, which had 

 itself turned inside out. In the centre the thickness of the primary me- 

 senterial septa is clearly traceable, then the pairs of the ovaria, partly at- 

 tached to the septa, and beyond those towards the periphery, the very 

 numerous craspeda, and then follow the tentacles, with their shrunken 

 tips ; — two of the threads extending beyond the periphery representing 

 the acontia. The craspeda are seen constantly winding up and down, like 

 worms, contracting and expanding, and thus shewing great vitality, but 

 I have not observed in them any rapid motions ; they are never ejected 

 through the cinclides. Examined under the microscope (see figs. 8 and 

 8a, pi. XI) their cnidce are seen to be arranged in two marginal rows, 

 lying with their longer diameter perpendicularly to the length of the 

 craspedum, and leaving in the middle a sort of a canal or a string, 

 which is filled with a cellular substance and a very large number of 

 pigment cells ; no larger cnidce, being visible in the centre. The cellular 

 substance probably assists in effecting the muscular motions. The cnidce 

 are distinguished by a considerable length, (the longest about g-g-oth 

 of an inch), being rather straight, generally attenuated at one end 

 and usually shewing in a slight curve an indistinct central line, indicat- 

 ing a moderately long but very thin ecthoreeum ; this latter is rarely seen 

 ejected, but if it is it appears to be about one-third longer than the 

 nettle-cell itself. The thinner ends of the cnidce slightly project on 

 the lateral marginal surface of the craspedal bands, giving them a 

 very fine ciliated appearance. Numerous pigment cells and others, are 

 also observable between the marginal cnidce. 



The true nature of the craspeda in the physiological economy 



