THE SPONGES. 66 



the line along which the lips of the terminal cup have coalesced, in what 

 may be spoken of as the preceding stage of growth. 



The arrangement of the tubular structures or ridges indicates that 

 when the terminal cup, which is inclined obliquely to the stem (Fig. 1, 

 Plate 8), divides, the lower half remains as a lateral cup, while the 

 upper half, now the terminal cup, grows so as to add to the stem of the 

 sponge. It moreover grows in the direction in which the cup lips last 

 fused, but the next line of such fusion occurs at about a right angle to 

 the last. The several steps in the gradual building up of the whole sponge 

 from a cup-like young stage thus seem to be marked out by these relicts. 

 The structures in question are indicated in Schulze's figure of this species 

 (Schulze, 1899, Taf XVII.). This method of continuous separation of 

 lateral cups from the terminal with formation of a seam is probably 

 universal in the family, and in my macerated specimens of Eurete, sp. 

 traces of such seams are found. Also in some of the Farrea specimens, 

 ridges are observable which correspond in position to the structures just 

 described for Eurete, but they are vague and of themselves would be 

 incomprehensible. 



If Eurete and Farrea colonies are ontogenetically developed from cup- 

 like young stages, as general considerations and the special structures 

 above described suggest, then the small cup-like species of Farrea that 

 have been described may be merely stages in the growth of larger complex 

 colonies. Bowerbank (1875, p. 273, Plate XXXIX. Figs. 1, 4, 5) describes 

 and figures several small cup or vase shaped Farrea skeletons from the 

 West Indies. To these he gives the name of F. pocilliim. 



In this subspecies, as in Schulze's specimens, there is very little anasto- 

 mosis between the lateral branches. The few instances involve a fusion 

 between the oral lips of adjacent and bifurcated branches. 



Schulze observed that in his specimens the dictyonal framework of the 

 terminal cups for a certain distance from the edge was Farrea-Wke, con- 

 sisting of but one layer of beams. In my specimens, the dictyonal frame- 

 work of the terminal cups, like that of the lateral cups, includes in general 

 two or more layers. And in parts of the extreme periphery, where the 

 edge seems to be unbroken, I find two layers. I have also, howe\'er, 

 found in the terminal cups quite small tracts, passing irregularly into the 

 two-layered condition, in which the framework consisted of but one layer. 

 Again in some of the lateral cups, in the stage of division corresponding 



