210 Mr. H. J. Carter on the Position of the 



which is the homologue of the ampullaceous sac in the sili- 

 ceous sponges, as above shown. But I desire to put forth raj 

 own views of the position of the ampullaceous sac and its 

 relation to the water-canals as deduced from the observations 

 above mentioned. 



Probably there is more than one aperture in the ampulla- 

 ceous sacs in manj instances, for I do not see how two could 

 be represented in the microtomized sections unless this had 

 been the case. Then, all I can state is, that there is pro- 

 bably an equal number of instances in which there is only one 

 that serves both purposes, viz. for the inception of the 

 nutrient particles and the exit of the refuse or unassimilated 

 material ; wdiich could thus be as easily effected as in a polyp. 

 I have already stated that I never could see any other vessel 

 connected with the ampullaceous sac than the excretory canal. 



It is very desirable, however, that more Avidespread obser- 

 vation on this subject should be made, for it appeal's to me 

 that the species of WilsoneUa which, in conclusion, I am about 

 to describe, is an unusually favourable one for such observa- 

 tions. At the same time I must say that all the more impor- 

 tant observations in the physiology of the Spongida that I 

 have made have been obtained by studying living specimens 

 directly and experimentally, which seems to me to be too 

 much neglected now for the description and classification of 

 dead species. But this, of course, necessitates a temporary 

 residence near the places where the freshwater and saltwater 

 species respectively grow. I began my study of the sponges 

 in this way. 



WilsoneUa echinonematissima, n. sp. 



Specimen small, without any particular form, being about 

 an inch in diameter each way and composed of a mass of 

 keratose, echinated skeletal fibre covered above by prominent 

 conuli projecting from a smooth surface. Consistence firm, 

 resilient. Colour sponge-amber. Surface even between the 

 conuli, which are large, obtuse, distant, and prominent, tied 

 together by the usual fibro-reticulated intervening structure 

 underneath a thin layer of small epithelial cells. Pores 

 grouped together in the epithelial layer over the interstices of 

 the fibro-reticulated structure. Vents not seen. General 

 structure from without inwards consisting of the thin epi- 

 dermal layer, in which the pores are situated, overlying a 

 comparatively thick one composed of cancello-clathrate fibrous 

 membrane whose intervals intercommunicate with each other 

 throughout, thus corresponding to the " subdermal cavities," 

 resting upon the body-structure of the sponge, which in its 



