316 PLATE LXXXIX. 



pedestal. In another species, Tethea Norvagica, we 

 find numerous pedicelled gemmules springing from all 

 parts of the parent sponge. 



This species is described in the same volume of the 

 ' Proceedings of the Zoological Society,' p. 121, plate 

 v, figs. 1825. 



The specimens under consideration vary more or 

 less from either of the preceding cases. Although I 

 have had a large number of specimens of Tethea 

 cranium through my hands, I have never observed an 

 external case of gemmulation although the interior of 

 the sponges abounded with those organs. The speci- 

 mens under consideration were sent to me by Mr. 

 Barlee from Shetland in the state in which they are 

 represented, excepting that one of them was divided 

 by me perpendicularly for the purpose of obtaining 

 sections to exhibit its anatomical structure, and it was 

 found that the skeleton, instead of radiating from the 

 centre of the young sponge was based upon the distal 

 extremity of the pedestal whence it radiated in every 

 direction. 



The spicula obtained from a small slice of the sec- 

 tioned specimen, fig. 6, were precisely of the same 

 description as those taken from adult specimens of T. 

 cranium with this remarkable difference, that the 

 porrecto-ternate defensive ones were some of them of 

 the same size and proportions as those of the adult 

 sponges, and others were as those of the gemmular 

 bodies, thus indicating the transition of the external 

 gemmule from the younger to the more mature stage 

 of its development. Many of the recurvo-ternate ones 

 were also in an immature state of development. In all 

 their anatomical characters these little specimens agree 

 so perfectly with the corresponding parts in the adult 

 specimens as to render their identification with the 

 adult unmistakable. 



