468 ASTROSCLERA WILLEYANA, THE TYPE OF A NEW FAMILY OF SPONGES. 



has tended. An examination of the base of this side {b) shows that this process has 

 occurred many times in the earlier stages. It appears that the upper (perforated) 

 surface of this specimen has shifted in the course of growth, the canals becoming 

 closed on one side while new ones have appeared on the other. The layer of cortical 

 (unperforated) skeleton which may be seen in the Funafuti specimen (Fig. A, 1) to 

 extend from the bases of the later formed bosses over the surface of the original 

 growth has probably a similar origin. 



The specific relationship of the specimens from two localities. As the soft tissues 

 proper to the organism are absent from the Funafuti specimen the question of its 

 specific relationship to those from Lifu may here be considered. Do they belong to 

 the same species, of which those from Lifu represent the younger and that from Funa- 

 futi a more advanced stage, or are they specifically distinct ? The scanty supply of 

 material prevents a definite answer being given, but the following points may be urged 

 in favour of the former view : 



The characters of the skeletal elements are, I believe, identical. 



Though the shapes of the organisms from the two localities are very different, there 

 is to be seen in the Lifu specimens a tendency to expand as they grow, which if carried 

 out might well lead to the formation of a structure like that which is called above 

 the original gi'owth of the Funafuti specimen. A similar change of shape occurs in 

 the coral Fungia, which in the young state is cylindrical and later expands into 

 a disc. 



The difierentiation of the efferent (?) canal system appears to be more complete 

 in the Funafuti specimen, but this is a character which might, as above suggested, 

 become more marked in proportion as the extent of the system to be drained increased, 

 and one of the Lifu specimens (Figs. I and 1, a) shows a distinct indication of it. 



The fact that the Lifu specimens (as stated below) contain eggs is an indication 

 that they have attained sexual maturity, but not that they are at the limit of their 

 growth. 



It appears that there is at present no sufficient ground for regarding tlie forms 

 from the two localities as specifically distinct. 



The Soft Tissues. The gelatinous layer above described as investing the ridges 

 of the skeleton, lines the openings of the canal system and extends as a sheet, 

 thinner in the centre, over the end of each canal (Fig. 8). A round pore is 

 frequently present opposite the centre of a canal (Figs. 7 and 11), but in many cases 

 the membrane appears not to be perforated at this point. The spaces at the mouths 

 of the canals are however in communication with one another, by lateral channels 

 through the jelly, beneath the surface membrane. 



The soft tissue can be traced for a short distance down the sides as a thin 

 layer, investing the outer surface of the animal. 



Besides the cells in which the spherules are formed, there are branched amoeboid 

 cells .sparsely scattered through the jelly (Figs. 18 and 19). The jelly, as well as the 

 organic basis of the skeleton, takes a faint blue stain with picronigrosin. 



