OF THE SPONGIAD^. 149 



ceived to be the male gemmule in T. cranium. I have 

 several other species of Tethea in my possession, but I have 

 not yet found gemmules in the interior of any of them. 



EXTERNAL GEMMULATION. 



In Tethea lyncurium we have gemmules produced ex- 

 ternally, which are perhaps much more entitled to that de- 

 signation than any of the reproductive organs previously 

 described. The fasciculi near the base of the Tethea are 

 protruded considerably beyond the surface of the animal, 

 and at the termination of each there appears a small mass 

 of sarcode, which assumes a more or less globular form. If 

 their bodies be immersed in Canada balsam and examined 

 microscopically, they will be found to contain not only the 

 spicula projected from the parent, but a second series, 

 which have been secreted in the mass which have assumed 

 the mode of disposition so characteristic of the skeleton of 

 the parent Tethea. I am indebted to my late friend Mr. 

 T. H. Stewart for this interesting fact, and for the speci- 

 mens illustrating it. They were found in Plymouth 

 Sound. 



Pig. 342, Plate XXV, represents one of these gemmules 

 with a portion of the skeleton fasciculus on which it is pro- 

 duced, under a linear power of 50. 



PROPAGATION BY SABCODOUS DIVISION. 



The fact of the resolution of the sarcode of the interstitial 

 tissues of Spongilla into small masses of unequal size and 

 variable form has long been known to naturalists, and that 

 when separated from the parent body each becomes capable 

 of locomotion, and of ultimately becoming developed into a 

 perfect sponge. Carter, in his valuable paper pubhshed in 

 the ' Journal of the Bombay branch of the Royal Asiatic 

 Society,' No. 12, 1849, has given a minute account of their 

 structure and motions when separated from the species 

 which form the subjects of his paper, and his descriptions 

 are in perfect accordance with the similar bodies separated 



