50 ART. 7. — T. TJIMA : HEXAC'TINELLIDA, IV. 



connective-tissue cells and the pinacocytes of the ÙMonaxonia and 

 the Triaxonia. The two kinds of cells just mentioned are l)oth 

 the outcome of the larval " dermal cells ", which in the Hexacti- 

 nellida seem very early to take the form of trabeculee. 



If I am right in the above assumption concerniuü; Ihc 

 morphological nature of the larval reticulum, the spaces in it or 

 the meshes are sim2:>le interstitial lacunœ, which later (after the 

 immigration of the external flagellated cells inwards to forui tlie 

 c]iam])ers) should come into free comnmnication with the exter- 

 nal world. From tliis standpoint it is exceedingly questional)le 

 if the fluid contained in them is to he regarded in the light of 

 a connective-tissue mesoglœa, Avhicli, moreover, is something 

 apparently totally nndeveloped in the adults (Contrih. I., p. 101). 

 It seems more likely that the fluid is simply imbil)ed water, — an 

 assumption which suggests itself as being by no means improb- 

 able. 



The reticulum can be traced, from the anterior region before 

 ]-eferred to, backwards into that lying posterior to the broadest 

 ])nrt of the larval body. In fact it may be said that the reticu- 

 lum pervades almost the entire inner mass. Only, in the more 

 extensive posterior region just indicated, forming about four-fifths 

 of the entire mass, it is not quite plainly visible, this being probablv 

 due to the crowded co-existence here of small and approximatelv 

 spherical cells. INIoreover, the meshes here are on the whole 

 consideraltly wider than in the small anterior region which lacks 

 the said cells. It may not be improper to consider that iu a 

 measure their greater width stands in relation to the presence 

 therein of the cells in question. 



These cells, which pro1)ably deserve to be called sim])ly the 

 archœocvtes, measure onlv 2-2 ^ ,"-. As in the case of the same 



