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



are about l-24tli and those in T. zetlandica about 1-1 6th of an 

 inch in diameter : thej are therefore easily visible to the un- 

 assisted eye, and hence I have been able to give the outlines 

 of a section of tig. 2 in fig. 13, which is pregnant with them, 

 while, every part having been drawn of the natural size, the 

 reader will, by reference to it, have nearly a facsimile of the 

 object itself. Most of the oviform bodies and many in the 

 section only just showing themselves above the level of the 

 sarcode, while others are on their edges, their outlines, of 

 course, are not all of the same size and shape. Whether the 

 compression, which, as will hereafter be seen, is confined to 

 the less-advanced forms, arises from the contracting effect of 

 the spirit on a globular form when fresh, or whether it is natural 

 to these bodies, I am ignorant, having never seen a TetJiya 

 under these circumstances while living. 



In Dr. Bowerbank's ^ British Sponges,' pi. 25. fig. 343, will 

 be found a monstrous representation of one of these oviform 

 bodies under the designation of " gemmule," which is only 

 surpassed by his description (vol. ii. p. 87), where he applies 

 the term " sexual " to them, and conjectures that one may be 

 the " female or prolific gemmule ;" but Dr. Bowerbank had 

 never been able to discover any " spermatozoa " in either ! 



As this is a kind of physiology which I do not understand, 

 let us go back to the term " oviform " first applied to these 

 bodies by their original discoverer, and see if we can trace 

 them from their earliest appearance up to the complete deve- 

 lopment of the full-formed young Tethya. But before enter- 

 ing upon this subject, it is desirable to premise a description 

 of the sponge-animal from which the ova are first produced, 

 and then the mode of sexual union by which impregnation is 

 accomplished. 



Last year I confinned Prof. James-Clark's discovery of a 

 " collar " round the cilium of the sponge-animal (Annals, 

 vol. iv. p. 1, pis. 1 & 2), and at the same time gave a full 

 figure of this body, which must now be regarded as the animal 

 of the sponge just as much as the polype is regarded as the 

 animal of the coral. 



Since then most of my observations on the " ultimate 

 structure of Spongilla^'' in which the animal was first pointed 

 out (Annals, 1857, vol. xx. p. 21, pi. 1), have also been con- 

 firmed by Prof. James-Clark in his description and illustration 

 of the American SpongiUa (American Journ. Sc. and Arts, 

 Dec. 1871, vol. ii. ; republished in the Annals, 1872, vol. ix. 

 p. 71, pi. 11, and in the Monthly Microscop. Journ. for March, 

 No. xxxix. p. 104). 



Shortly describing the animal, animalcule, or infusorium of 



