38 Memoirs of the Indian Museum. [Vol. V, 



Those of the larger type have small subglobular heads which are not separated 

 from the shaft by a constriction. As a rule the heads are only prevented from being 

 spherical by the fact that they are flattened at the point at which they are attached 

 to the shaft, but trilobed, acorn-shaped and other forms occur among them (fig. 5) 

 and these are often asymmetrical. The shafts are long, relatively slender and as a 

 rule straight, if curved but slightly so and usually only towards the distal extremity. 

 The maximum diameter is already attained at the point at which they are joined 

 to the head and does not diminish until near the other end, at which the shaft tapers 

 to a very fine point. The greatest length of the spicules of this type is 0-44 mm. , 

 the greatest thickness of the shaft 00117 mm. and the diameter of the head about 

 o'0i2Ô mm. Some spicules that belong on account of the relative slenderness of 

 their shafts to the same type are rather smaller and a few greatly so, being not more 

 than 0-105 mrn - l° n g- The diameter of the shaft varies considerably. 



The second type of spicule has the shaft as stout as that of the largest spicules, 

 but the maximum diameter is situated as a rule near the middle of the length 

 and the shaft tapers towards the head. The length of the shortest spicules of this 

 type is not more than 0*098 mm., but it may be as much as 0*147 mm - an d is usually 

 about 012 mm. 



Spicules of the first type are found in abundance throughout the sponge, but 

 those of the second occur singly in the central parts only. 



The living sponge, in both phases, is of a bright sulphur- yellow colour, which is 

 evenly distributed throughout its substance and disappears rapidly in spirit. The 

 consistency is soft and somewhat elastic. 



The oscula are small and scattered; they are not connected, as in the two 

 species of Laxosuberites found in the lake, with a regular system of subdermal canals, 

 but a few irregular exhalent channels in this position sometimes open into them. As 

 a rule these canals are more deeply buried, often running for some distance parallel 

 to the surface in the choanosome and opening not directly into the osculum but into 

 vertical canals that extend downwards from it. The pores are minute and not 

 confined to restricted areas ; the vertical lacunae into which they open are small and 

 the structure of the whole inhalent system is obscure. 



The position of the main exhalent channels, combined with the rather dense 

 structure of the outer parts of the sponge, indicates some approach to the differen- 

 tiation between ectosome and choanosome that reaches a much higher degree of 

 development in Pseudosuberites. There are always, moreover, horizontal spicules in 

 the external parts, though this is much more marked in certain conditions of the 

 sponge than in others and in some cases their number is very small. 



There is a stout horny membrane at the base of the sponge. 



Phase A. 



The skeleton in this phase is fragile and the exercise of pressure immediately 

 reduces it to an amorphous state. If sections be made of carefully preserved mate- 

 rial a definite structure is apparent, especially if the part sectioned does not contain 



