Mr. H. J. Carter on the Subsjjherous Sponges. 21 



lyncurium or in Pachymatisma Johnstonia ; and of course 

 they could not, if present, be detected in the dried state of 

 Geodia arahica ; nor has any one ever described such bodies 

 in either of these species ; but gemmules have been described 

 and figured in Tethya cranium by both Johnston and Bower- 

 bank, and therefore it is interesting to find something of the 

 kind in the Arabian representative of this sponge. 



Two kinds of gemmules, with marked difference, have been 

 described and figured by Dr. Bowerbank in T. cranium (Brit. 

 Spong. pi. 25. figs. 343, 344) ; but when he adds (vol. ii. 

 p. 87) that " It is highly probable that this marked difference 

 in structure is sexual, and, from the more highly developed 

 condition of the second or largest form, that it is the female [!] 

 or prolific gemmule," it can only be hoped that Dr. Bower- 

 bank's illustrations are, as usual, much better than his physio- 

 logical interpretations. 



We use the terms " sperm " and " germ-cell " for the male 

 and female elements of the true or impregnative process of 

 generation ; but the term " gemmule " stands for " bud," in 

 which no one has yet detected more than a portion of the 

 product evolved from a combination of the male and female 

 elements of generation. 



In short, the true or impregnative process of generation in 

 the Sponge has not yet been made public, even if ever disco- 

 vered. Lieberkiihn (/. c.) has stated that he has seen cells 

 filled with spermatozoa in Bpongilla ; Prof. Huxley has de- 

 scribed and illustrated what he considers to be spermatozoa in 

 an Australian species of Tethya ; and I have latterly en- 

 deavoured to throw more light on the subject by pointing out 

 the probability that in the freshwater Rhizopoda {e.^.Dijflugia) 

 the nucleus furnishes the sj'temi-y and some other part of the 

 body of Difflugia the ^erwi-cells, which produce the new ge- 

 neration (Annals, 1865, vol. xv, p. 172). But how far this 

 may be con-ect in itself, or how far it may apply to the gene- 

 rative process in the sponges, remains still to be discovered, 

 since at present this process is as much a mystery as the ge- 

 nerative process was in the stipitate Fungi before OErsted and 

 Karsten demonstrated that it took place through the union of 

 male and female cells growing out of the mycelium. 



I observe, however, that much of the sponge-substance on 

 the surface of T. arahica is charged with minute nucleated cells 

 about 2-6000ths of an inch in diameter, frequently grouped to- 

 gether, as if the group had been developed in one cell — and that 

 the substance so charged is especially supported on the rays of 

 the trifid spicule, as shown in fig. 20, PI. II. Neither could 

 I help being struck with their resemblance to similar nucleated 



