172 Prof. A. Dendy on 



referable to Trngosia iufundibuliformis. Two of these I 

 examined niicroscopically. The lir.^t was labelled, in Bower- 

 bank's writing, " Halichoudria infundihuHformis .]o\\\\%i.'\ to 

 which had been added, a|)i)iirently in Carter's writing, '' T. S." 

 and " Isodictya inf. Bk./' suggesting that Mr. Carter re- 

 garded this as the typc-speciiueii of the species as accepted 

 by Joiiuston and Bowerbank. The second was labelled 

 "Isodictya infundibuli/onnis Bk." and '"'■ Halickondria in- 

 fuiidibulifonnis Sowerljy.'^ lioth of these specimens had 

 the typical external form and both contained trichodrag- 

 mata. There can be no doubt that they are specifically 

 identical with the specimens obtained by Professor Herd- 

 man from the Minch. 



I think we may now state confidently that the common 

 British species upon which Gray's genus Tragosia was founded 

 contains trichodragmata as constant and characteristic con- 

 stituents of its spiculation, and may thereby be distinguished 

 much more sharply from Pliakellia than was formerly 

 p!)ssible. The fact that these spicules have been com- 

 pletely overlooked by previous observers may probably be 

 accounted for by their having examined only dry specimens, 

 in which the shrinkage of the soft tissues makes it much 

 more difHcult to recognize them. 



I have already, on more than one occasion [1916, 19.21 a], 

 called attention to the curiously sporadic distribution of this 

 type of microsclerc amongst the Tetraxonid Sponges, and 

 suggested that it has probably arisen again and again in the 

 course of evolution through parallel mutation. I have also 

 doubted its v.'»lae for purposes of generic distinction, and 

 bc^n^ I Tear, somewhat inconsistent in this respect. Thus 

 I have refrained [1921 n] from separating Cinachyra eury- 

 stoma, which possesses trichodragmata, from the remaining 

 nineteen species of the genus, which possesses none, while, 

 in the same memoir, I refused to admit into the genus A.ci- 

 nella a species (" Thinacophora" diirissima) which possesses 

 trichodragmata, and also suggested that the presence of these 

 spicules may be used as a means of distinguishing the genus 

 Mycale from yEgagropila and Ef^perella. I have suggested, 

 in short, that each case should be treated on its merits, 

 ■without attempting to lay down a general rule. Where a 

 generic diagnosis is quite inadequate, as in the case of 

 Tragosia, the presence or absence of trichodragmata may 

 well be taken into consideration. 



Hallmann [1910-17], a few years ago, published a 

 revision of the genera of so-called Axinellid«e containing 

 microscleres, in which he mentions a considerable number 



