382 Mr. H. J. Carter on the Nutritive and 



descriptions respectively), together with my better acquain- 

 tance with the subject, that the smallness of the monociliated 

 bodies which I figured as zoosperms, when compared with the 

 " eared " (collared) monociliated sponge-cell, is so much in 

 favour of what I had conjectured, that little doubt can be 

 entertained by those familiar with such bodies that they 

 really icere the zoosperms of Spongilla. The time of their 

 appearance in the Spongilla, their mode of progression, and 

 their inferior size, if we do not admit the absence of the ear- 

 like processes (collar) also, must satisfy the most fastidious 

 mind that they could have been nothing more or less than 

 " zoosperms." 



About the same time also, viz. 1856, Lieberkuhn dis- 

 covered and described, with illustrations, the swarm-spore 

 (embryo) of Spongilla and its development, which Grant, as 

 above stated, did of Halichondria incrustans in 1826 (no. 5, 

 pp. 9-14 and pp. 405-413, pi. xv. fig. 35). 



Finally, F. E. Schulze, in 1877, pointed out the existence 

 of spermatozoa in Halisarca lobularis in a much more satis- 

 factory way than had hitherto been done, as testified by his 

 descriptions and illustrations (no. 17, p. 24, Taf. iii.), toge- 

 ther with some of his beautiful preparations, which, through 

 his great kindness, are now in my possession. 



They occur in the form of globular groups ("Sperma- 

 ballen"), so like in size and appearance to the ampullaceous 

 sacs (" Wimperkorbe ") that, but for the smallness of the 

 monociliated colourless head of the former, they would be 

 almost undistinguishable from the larger monociliated and 

 collared form of the latter, both being polymorphic and bearing 

 the proportion of about 1 to 5 (compare Schulze's fig. 12, Taf. 

 ii., with fig. 17, Taf. iii., both of Avhich are magnified 800 

 times). In size the two look respectively very much like the 

 so-called microspores and macrospores of Algae; and at first 

 one would be inclined to think that reproduction was similarly 

 accomplished by their union. But another factor steps in here, 

 viz. the unciliated sponge-cells of the parenchyma or meso- 

 derm, which MetschnikofT has shown to take in nourishment 

 equally with the monociliated cells of the ampullaceous sacs, 

 or, at all events, to do so when the latter do not. And here 

 (in the mesoderm) it is, that the ova appear (see Schulze's 

 satisfactory figure of the eggs in Sycandra rapkanus, H., 

 no. 14, Taf. xviii. fig. 2) — a fact that all who have studied 

 any of the calcareous sponges in spring (that is, during the 

 reproductive period) must be well aware of, although Grant, 

 who first mentioned this, observed it (Halichondria incrus- 

 tans) during the autumn (" October and November ") (no. 1> 



