﻿SPONGES.- HALLM ANN. j -,q 



and scaitcrcd in the iiyound-substance ; [iv.) shorter sub- 

 tylostyJi {or styli) of scarcely one-half the length of the 

 preceding, almost entirely restricted to the dermal layer. 

 A larger or smaller proportion of fJic mcgascleres (u), 

 {Hi.) and {iv.), are provided 7vith a minute basal spina- 

 tion : this spination is the normal condition of dermal 

 styli and is of least frequent occurrence amongst the 

 principal styli. Microscleres : — {i.) Palmate isocheltx of a 

 single kind varying in maximum length in the different 

 forms of the sponge from 20 to 2^ n ; {ii.) angiilately 

 curved toxa 60 to 80 pi in length, and 2 to 2.f; ]i in 

 diameter. 



Introductory Remarks. — .\s the result of an examination of 

 the figured specimen of Thalassodendron riibcns var. lamella, 

 and of undoubted specimens of T. rubens var. dura { = Clathria 

 rubens), I find that Lendenfeld has confused the descriptions 

 •of these two sponges. The descriptions of their external 

 <:haracters are proper, but those of their skeletal characters 

 should be interchanged. To further add to the confusion, 

 Whitelegge, overlooking the essential points of difference 

 between the two, united them, together with T. brevispina, as 

 a single species, Clatliria rubens; of the five specimens whose 

 spicular characters he has separately described — though not 

 •quite accurately — the second (labelled ''Thalassodendron 

 rubens var. dura, No. 343"), as well as the third and fifth, 

 belong to the present species {vide Whitelegge, Loc. cit., 

 pp. 86, 87). 



Description. — 



(a) I'vpical variety. 



The sponge is frequently — except for the presence of mar- 

 .ginal digitations — perfectly lamelliform. More usually, how- 

 ever, growth proceeds by the rapidly-repeated multiplication — 

 always chiefly or entirely in one plane — of ascendant, cylindri- 

 cal or slightly compressed, anastomosing branches, and results 

 in the formation of a reticulated or fenestrated flabelliform 

 -expansion. From this, a more or less continuous lamella may 

 in some cases be secondarily produced, through the gradual 

 obliteration of the interspaces by vertical ingrowth. It is 

 either owing to this latter mode of origin or because an actual 

 separation into branches is not quite fully accomplished, that 

 the surface in lamelliform examples is often, as Lendenfeld 

 states, "slightly groo\ed." In some instances the sponge 

 shows a marked disposition towards a freely branching habit, 

 but in no observed case is there, as is usual in the variety 

 multiporus, an entire absence of anastomosis or of confluence 

 of branches. The specimen of 2\ rubens var. lamella, figui-ed 



