132 ANATOMY AND PHYSIOLOGY 



On a careful consideration of the descriptions of the 

 ciliated cells seen by the authors I have quoted above, it 

 strikes me forcibly that the so-called zoosperms and sper- 

 matozoa of Carter and Huxley are identical in origin and 

 purpose with the similar organs described by Lieberkuhn, 

 and those found in situ and in action in Grantia compressa, 

 and in truth that they are the homologues of the breathing 

 and feeding organs of the zoophytes and more highly 

 organized animals. 



REPRODUCTION. 



The ovaria in sponges exhibit considerable variety in 

 shape and structure. The most familiar form is that of 

 Sjjongilla Jluviatilis, represented in Fig. 317, Plate XXII, 

 in its natural condition. 



These bodies have hitherto been usually designated as 

 genmmles, but this term appears to be inappropriate. Each 

 of them contains numerous minute vesicular, round or oval 

 molecules, which are discharged from the foramen in suc- 

 cession, and each of these appears to be capable of pro- 

 ducing a sponge. The terms ovarium and ova are there- 

 fore more in accordance with the rules of modern nomen- 

 clature, and this alteration in their designation is the more 

 necessary, as I shall hereafter be enabled to show that in 

 Tethea lyncurium propagation by true external gemmatian 

 in that species at least really exists. I propose, therefore, 

 for the future that all such large vesicular organs containing 

 numerous molecules or ova capable of reproducing the 

 species, and of being successively ejected from the sponge, 

 should be designated ovaria and ova, and that the term 

 gemmule should be restricted to the isolated bodies which 

 pullulate from the internal or external surfaces of the parent, 

 and by ultimate separation become each a distinct indi- 

 vidual. 



The reproductive powers of the Spongiadae have been 

 treated on to a considerable extent by preceding authors, 

 and the amount of our information on this subject is, I 



