424 Mr. H. J. Carter on the Reproduction of Sponges. 



malcule as well as that of the Diffiugice and Amoehce. We 

 know that they all possess the power of polymorphism, and 

 take in crude material for nourishment, but that the former 

 differ from the latter in being infinitely smaller, in possessing 

 a cilium, and in living in communities. However, if we view 

 the sponge-animalcales as but an inferior grade of Amoebce, as 

 we view the compound Tunicata as inferior grades of the great 

 separate Ascidians, then the presence of the cilium in the 

 sponge-cell finds its explanation in the fact, according to 

 my observations, that the young Amoebce begin life with a 

 cilium, which is afterwards retracted. (Annals, 1863, vol. xii. 

 p. 48, and 1864, vol. xiii. p. 21, pi. 2. fig. 19. 



We have also become acquainted with the phenomenon 

 called zygosis in the Difflugice^ and its probable consequences, 

 including the formation and development of the oviform bodies 

 into forms like the parent. Let us now see how far any thing 

 in the sponges may present itself to us like the latter. 



In Dec. 1869, long before I knew any thing, from actual 

 observation, of the form of the sponge-animal, as described by 

 Prof. James-Clark, I had a very small Halicliondria simulans^ 

 Johnston {i. e. not more than a quarter of an inch in diameter), 

 under microscopic observation, in a watch-glass with sea- 

 water, for several days ; and during this time I repeatedly 

 assured myself of the form and measurement of all its elemen- 

 tary parts, which, with the position of the spicules, were care- 

 fully drawn in my journal, upon the scale of l-6th to l-6000th 

 of an inch. I have therefore now the most reliable informa- 

 tion on this subject, particularly as these observations and 

 drawings were again repeated with similar results on another 

 specimen of the same species in January 1870. 



Among these elementary parts there are figures of the con- 

 jugation of cells somewhat larger than the sponge-animals of 

 the " groups," but bearing such a strong resemblance at once 

 to the form of the sponge-animalcule among the sponges, and 

 to zygosis among the Diffiugue^ that little doubt can be enter- 

 tained of the latter being identical. 



I have therefore selected for publication that figure (8) which 

 best illustrates the facts, as the others, although equally con- 

 vincing, are more or less complicated with pseudopodial pro- 

 longations. 



In this figure we observe distinctly the bodies (a a) of the 

 two sponge-animalcules in conjugation or zygosis, united by 

 their rostra {hh)^ drawn upon the scale, as just stated, of 

 l-6th to l-6000th of an inch. This would give the ordinary 

 size of the sponge-animalcule of the calcareous sponges, which 

 appears to be about double the size of that of the siliceous 



