174 NATURE AND AFFINITIES OF THE SPONGES. 



of spore-production, as observed in Leiicosolenia coriacea, are given at 

 PL X. Figs. 1-7, while, for the purposes of future reference and comparison, 

 sections of this sponge and the other species named, exhibiting similar 

 reproductive features, were preserved with osmic acid and other suitable 

 media. 



As a substantial proof of the derivation of these variously formed 

 spore-masses from the typical collar-bearing units, examples were observed, 

 as represented at PI. X. Figs. \a and 2b, in which these zooids had with- 

 drawn their characteristic collars and flagella and assumed a quiescent 

 or encysted state, while in closely adjacent examples they had become 

 resolved into the spore-masses under discussion. Near these again, 

 the spore-masses in their disintegrated state, or higher developmental 

 phases, were found, as shown at Fig. 2, d d, scattered through the sub- 

 stance of the thin, transparent cytoblastema. In one point only was the 

 character of the spore-masses, as now examined with the highest available 

 magnifying power, found to differ from that assigned to them in their 

 earlier record already quoted. At that time, in the case of Leiicosolenia 

 botryoides, a delicate capsular investment or sporocyst was presumed to 

 exist. No trace of such an investing element could, however, be detected 

 in L. coriacea. The entire body of the collared sponge-monad, after 

 assuming a quiescent state, divides by segmentation into a mass of 

 characteristic microspores, and these falling asunder, become distributed 

 throughout the hyaline cytoblastema. It might have been suggested, and 

 was indeed at first anticipated by the author, that the spore-masses, as here 

 figured and described, might have been derived from some protozoon or 

 protophyte which had established itself as a parasite or commensal within 

 the canal-system of the sponge-body. The unmistakable import of these 

 structures as integral constituents of the latter, is, however, abundantly 

 demonstrated by their undeviating recurrence and mode of distribution in 

 the sponge-body, even when obtained from the most remote localities. 



In this connection it has to be recorded that spore-masses, presenting 

 the same form, size, and character, have been encountered by the author 

 without any exception in examples of Leucosolenia coriacea, personally 

 collected and examined in the living state, derived from Teignmouth, 

 Ansty's Cove, Falmouth, and other points on the Devonshire and Cornish 

 coasts, and also from various stations in the Channel Islands. Corro- 

 borative evidence relating to this species has likewise been recently 

 obtained from an independent and altogether unexpected source. In 

 vol. iii. page 8, of Dr. Bowerbank's ' Monograph of the British Spongiadas,' 

 1874, bodies of a precisely similar character, though connected with a 

 different title, are described as occurring in specimens of this sponge col- 

 lected in Shetland and remitted, preserved in spirit, to the author by the 

 Rev. A. M. Norman. Dr. Bowerbank's account of these spores is as follows : — 



"On examining the sponge microscopically I found it contained an abundance 

 of gemmules. They were exceedingly numerous on the inner surface of the dermal 



