Mr. T. H. Huxley on the Anatoimj of the genus Tethya. 371 



are, so far as I am aware, the only authors who give any detailed 

 account of the genus Tethya. 



Of the tw<j species described by the latter, T. Lyncurium ap- 

 proaches nearest to the present species ; the only difference being, 

 that while the former is yellowish white, the latter is deep red, 

 and that the stellate bodies, scanty in the former, are very nume- 

 rous in the latter. 



However, pale specimens were frequent among the deep red 

 ones — without any other apparent difference — and the presence 

 of more or fewer stellate bodies is a mere question of degree. 



MM. Edwards and Audouin describe currents traversing the 

 " oscules " of the Tetiiya similar to those of a sponge. I did not 

 obsei-ve pny cui rents, but I do not doubt their existence. 



Dr. Johnston says [op. cit. p. 82), " Tlie propagation of Tethea 

 is by means of sporules or gemmules generated within the sarcoid 

 matter. The latter resemble the parent sponge in miniatm-e, but 

 they have no distinct rind or nucleus, being composed of simple 

 spicula woven together by albuminous matter." 



I did not observe such " sporales or gemmules " in any of the 

 specimens I exair^ined, but it can hardly be doubted that these 

 bodies are I'lerely further developments of the " ova " which I 

 observed ; and as I found spermatozoa, it will follow, that the 

 Tethyce are reproduced by a process of true sexual generation. 



It would be most interesting to ascertain whether the " gem- 

 mules " of sponge take their origin in a similar way, and whether 

 true sperutatozoa are developed here also. 



The specimens of Tethyce observed presented several prominent 

 tubercles upiui their surface, perforated by irregular apertures, 

 from which a liquid exuded when the animal was taken out of the 

 water. 



"When there was only one or two of these tubercles, the external 

 resemblance to some forms of Cynthia was very great. 



On cutting across one of these bodies, it was seen to be solid, 

 and composed of three distinct substances ; \iz. a central whitish 

 spherical mass, a deep red cortical substance, and between these 

 two, forming the largest part of the body, a yellowish red inter- 

 mediate substance, sharply separated from both the central and 

 cortical substances. 



The two latter were united by radii of a silvery whitish colom*, 

 which ran. tl>rough the intermediate yellow mass, and became lost 

 in the cortical portion. 



Small canals took their rise at the apertures already mentioned, 

 and penetrating the cortical substance, ramified irregularly 

 through the intermediate substance, reaching as far as, but not 

 penetrating, the central substance. They appeared to be lined 

 by a veiT delicate smooth membrane. 

 ^ ^ 24* 



