148 ANATOMY AND PHYSIOLOGY 



diligently for spermatozoa in both forms of gemmule and 

 in the surrounding sarcode, I have not been able to detect 

 anything resembling them. But that such bodies do occur 

 in some species of Tcthca appears to be the case, Professor 

 Huxley having described and figured bodies which he 

 believed to be spermatozoa in a paper published in the 

 'Annals and Mag. Nat. Hist.' Second Series, vol. vii, p 370, 

 plate 14, as occurring in a species of Tetltea found in one 

 of the small bays in Sydney Harbour, Australia. The 

 gemmules represented by Pig. 343, Plate XXV, consists of 

 (a) one of the larger and supposed prolific gemmules, and (b] 

 one of the presumed male gemmules in situ, X 108 linear. 

 Wherever the former occurs, the latter appear always to 

 accompany them in the proportion of about two or three to 

 one. They are not seated like the ovaria of Geodia at the 

 surface of the sponge, but are always found on the inter- 

 stitial membranes at a considerable depth within the 

 sponge. The immersion of the specimen in Canada balsam 

 has rendered the marginal lines of the gemmules undis- 

 tinguishable from the surrounding sarcode, but their 

 natural boundaries would be just beyond the extreme 

 points of the spicula. 



Fig. 344, Plate XXV, represents one of the larger gem- 

 mules in its natural condition and separated from the 

 sponge, by direct light and a linear power of ^0. 



The reproductive bodies in the Tethca, described by 

 Professor Huxley, do not resemble those in T. cranium ; 

 no spicula are either described or figured as existing in 

 them, and in these respects they appear much more to 

 resemble the reproductive organs described by Dr. Grant 

 as existing in the Halichondraceous sponges of the Firth of 

 Forth. But I am not surprised at this discrepancy, as in 

 Tetlica simillima, Bowerbank, MS., in the collection of the 

 Royal College of Surgeons, from the Antarctic regions of 

 the South Sea, a species very closely resembling T. cranium, 

 the gemmules are so like those of the latter species as not 

 to be readily distinguished from them in their natural con- 

 dition ; but when microscopically examined, not the slight- 

 est trace could be found of the smaller, and what I con- 



