Reproductive Processes of Sponges. 381 



from the simple fact that these unfavourable circumstances 

 take place before one's eyes when the Spongilla or any other 

 sponge is torn to pieces ; while Metschnikoff states that, on 

 the other hand, when the favourable circumstances were 

 renewed (" erneuertem Wasserwechsel "), not only the cilium 

 but the ampullaceous sac ( <l Wimperkorb ") was remade in the 

 parenchyma of a young Spongilla. 



I cannot say, however, that the sponge-cells of Spongilla 

 lose the cilium in the winter in the tanks of the island of 

 Bombay, perhaps because the temperature then and there is 

 about that of our midsummer, since the last mention of it in 

 my ' Note-book,' together with an illustration in which the 

 " ear-like processes " (collar) are represented, is dated " 9th 

 January, 1859," just after my paper on the subject had been 

 published in England (no. 8, p. 14, pi. i. figs. 12-14). 



Reproductive Process. 



While on the subject of alimentation, it might be as well 

 to briefly enumerate the facts known in connexion with repro- 

 duction, since the latter is chiefly dependent on the former 

 process. 



As early as 1826, my late kind and talented teacher Prof. 

 Robert Grant described and illustrated (among his imperish- 

 able records of the Spongida) the embryo (swarm-spore) of his 

 Spongia panicea = Halichondria incrustans, Johnston, begin- 

 ning with the ovum " lying in the recesses of the parenchy- 

 matous matter," following its development into the ciliated 

 embryo, its exit afterwards through the excretory cell-system 

 and subsequent fixation, finally ending in the full develop- 

 ment of the young sponge (no. 1, pp. 127-133, and p. 140, 

 pi. ii. figs. 26-29) . 



In 1854 I described and figured minute monociliated bodies 

 which were observed in Spongilla at Bombay in the month 

 of July, and conjectured to be zoosperms (no. 4). Afterwards 

 Lieberkuhn described and figured undoubted spermatozoa in 

 Spongilla in July, at Berlin (no. 5, pp. 17, 18, pi. xv. fig. 34, 

 and pi. xviii. figs. 10 17), previously observed by Mttller 

 (no. 5, p. 19). 



That Lieberkuhn should have identified my description and 

 illustrations with Trachelitis trichophorus, Ehr., I could never 

 understand, because he must have known that the former 

 carried the cilium behind, and Trachelitis carries its cilium in 

 front. Moreover, although I have hitherto been inclined to 

 doubt if they really were spermatozoids or the common mono- 

 ciliated sponge-cell, I now observe, by the measurements 

 of both (which have fortunately been published with their 



