278 RECORDS OF THE AUSTRALIAN MUSEUM. 



What may be a different phase of the same species differs from 

 the above in having the capsular menbrane much less distinct 

 in the presence of numerous pigment granules in the intra- 

 capsular plasm. There is a similar lobed space representing the 

 oil-globule, but it does not give off the narrow radiating channels, 

 and it may be simple and rounded. The Algte are not in any 

 way specially related to the zooids. 



COLLOZOUM ARCUATUM, Sp. nov. 



(Plate liii., figs. -Jta-ic). 



In this species, in which the form of the entire colony is un- 

 known, the zooids are elongate and sausage-shaped. Each 

 contains about twenty nuclei which are axially situated in a mass 

 of vacuolated protoplasm with pigment. Within the capsule are a 

 number of pigmented bodies of irregular shape and varying size. 

 There are one or two oil -globules. 



There are woXanthellceoi the ordinary character, their place being 

 taken by a number of problematical bodies (figs. 4a, 4b, and 4c), 

 many of which are in close apposition with the capsules of the 

 zooids, while others lie in the intermediate spaces. The foundation 

 of each of these is a spherical cell with a centi'al nucleus, a few 

 large rounded granules in the cytoplasm and vacuoles. Arranged 

 around the surface of the cell, which appears to have a distinct 

 cell-wall, are a varying number (usually six to twenty) of bright- 

 looking bodies of somewhat variable shape, usually concavo-convex, 

 often with one or two grooves or notches. 



The resemblance which undoubtedly exists between the bodies 

 above described and the " extra-capsular bodies " described in 

 detail by Brandt is a purely superficial one. The latter are 

 derived fi-om the zooids, and appear to represent a phase in a 

 specidl process of anisosporous division. The bodies now under 

 consideration, on the other hand, represent a phase in the life- 

 history not of the Radiolarian, but of the Xaiithellae. These 

 bodies in fact correspond (as far as can be determined in the fixed 

 specimen) in every respect with ordinary Xanthellae with the 

 addition of the small bright objects symmetrically arranged around 

 each. 



In a few cases (PL liii., fig. 4b) the bright bodies are repre- 

 . sented by an almost unbroken layer of the bright substance. 



