24 THE VOYAGE OF H.M.S. CHALLENGER. 



these bands are disposed iu rows, intersecting approximately at right angles, at an 

 average distance of 0'06 mm., and united further by stronger basal strands, a lattice-like 

 pattern results, in which the meshes are approximately rectangular or slightly rhombic 

 in form. As to the nature of the somewhat strongly refracting and slightly stained 

 connecting strands, of which the stronger cross at right angles, while the finer branches 

 are irregularly reticulate (PI. LXII. fig. 8), I have not been able to come to a perfectly 

 clear decision. I have little doubt, however, that we have here to do with the 

 anastomoses of protoplasmic processes from adjacent cells. Each cell seems to be 

 connected with its four neighbours by one main connecting process and several fine 

 lateral branches (PL LXII. figs. 7, 8). 



The connective substance, which forms the main framework of the soft body, does not 

 differ essentially from that of most other siliceous Sponges. In the hyaline, somewhat soft 

 matrix, two kinds of cells can be distinguished, namely, (a) simple stellate or spindle- 

 shaped connective-tissue cells with little protoplasm, and a small oval nucleus, and (6) 

 larger cells with clear vesicular nucleus, and with a more or less abundant accumulation 

 of refracting, intensely stained granules of various sizes. As a rule, these granules lie 

 loosely beside one another, and may be included in lappet -like processes of the cell 

 (PI. IV". fig. 8, and PI. LXII. fig. 8). Sometimes, however, they are united in firm 

 clumps. Occasionally I found them brownish or yellow in colour. As I have previously 

 noted, I regard these bodies as reserve nutriment, analogous to fat or starch. Small 

 groups of round cells occasionally occur, but their import is not known (PI. LXII. fig. 8). 



All the skeletal structures belong exclusively to the connective-tissue. On the 

 surface of the spicules there is a more or less distinct thin layer of hyaline matrix, the 

 so-called spicular sheath, which, on specially thick needles, is seen as a finely fibrous 

 membrane. In the connective substance, finally, the genital products occur, the sperm 

 masses and ova, in more or less abundance, and usually in the same individual. The 

 sperm masses, both in young and mature stages, are exactly like those of other siliceous 

 Sponges, such as Reniera. In their immature form the ova are indistinguishable from 

 connective-tissue cells. They subsequently increase in size and develop refi"acting yolk 

 granules, and exhiint a very characteristic aspect owing to the enlargement of the nucleus. 

 It is remarkable that in the adult (0"3 mm. in diameter), irregularly roundish ova of 

 Euplectella asjiergillum, along with which ripe sperm masses also occurred, the nucleus 

 was situated not in the ovum itself, but lay freely in a superficial depression into which 

 it had been squeezed. This expulsion of the nucleus was probably the result of the 

 drastic preservative treatment. 



It is curious that I have never been able to discover any distinct segmentation stages. It 

 would not, however, be justifiable to jump to the conclusion that the ova leave the body of 

 the Sponge as such, and undergo subsequent development outside the mother organism. 



As to the developmental history I am only able to communicate a few observations. 



