HOLOTHURIANS OF KEW ZEALAISTD. 31 



The typical spicules (figs. 9-11) are described by Theel as 

 " wheel- or cup-shaped deposits," and his figures leave no doubt 

 a.s to their identity with those examined by me. I should prefer 

 to describe them, however, as rings, which enclose a cross on the 

 one side and a square on th.e other. The margin is undulating, 

 curving in at eight points, where the cross and square are 

 attached. The diameter of the ring is about 0*055 mm. These 

 spicules are very abundantly scattered through the integument, 

 forming an almost continuous crust. 



As Theel has already pointed out, the spicules around the 

 anus differ from those elsewhere, being irregularly branched or 

 reticulate (Pi. 3. figs. 12-14). The tentacles contain only a few 

 small reticulate plates lying near their bases. 



This Holothurian is very remarkable for the brownish-red 

 ccelomic fluid, which bears many points of resemblance to human 

 blood. Under the microscope it is seen to consist of a colourless 

 liquid in which numerous corpuscles float. The most conspicuous 

 of these are spherical bodies (PI. 3. fig. 15) of a brownish-yellow 

 colour, and about a quarter as large again as human red blood- 

 corpuscles. These are extremely numerous, and sometimes 

 appear polygonal from mutual pressure (PI. 3. fig. 15 a). They 

 are mostly of about the same size, though some are a good deal 

 smaller than the majority. Each contains, as a rule, one or a 

 few highly refractive particles. A 5 per cent, solution of 

 common salt causes the cell-contour to become wrinkled, but 

 they never appear flattened like human red corpuscles. 



Colourless corpuscles also occur in the coelomic fluid ; these 

 appear to be of two kinds, some being only slightly smaller than 

 the brown corpuscles and coarsely granular, while others are only 

 of about half the diameter of the brown corpuscles, and fiuely 

 granular. The coelomic fluid does not coagulate on exposure to 

 the air, but does so in alcohol. 



The above observations were made on fresh specimens which 

 had been out of the water for some little time. 



The only kindred observations known to me are those of 

 Howell, who describes* hsemoglobin-bearing corpuscles in the 

 water- vascular and perivisceral fluids of Thyonella gemmata. 

 Howell has also referred to the existence in this species of two 

 kinds of colourless corpuscles ; and the structural diff"erences which 



* Howell, W. H. Studies from the Biol. Lab. of Johns Hopkins Univ., 

 Baltimore, vol. iii. p. 284. 



