232 DISCOVERY REPORTS 



in thickness at the base. It is formed of two distinct layers which can easily be separated 

 one from the other. The inner layer forms the smooth lining of the cavity and is 

 occasionally beset with horizontal bars which run across the cavity. This dark reddish- 

 brown layer is surrounded by a thicker outer layer of a lighter tint. 



The main stem and secondary branches bear along their sides a number of short 

 branches each of which carries a single ostium at its tip. The ostia are almost circular 

 and each has four short spines at its edges. These spines, which are pointed, may be 

 forked. 



A unique feature of this colony is the dark reddish-brown colour of the coenoecium 

 which by itself might serve for regarding this as a new form of C. Jiodgsoni. 



The small specimen obtained from station 187 is represented in PI. XXXIII, fig. 5. 

 From such a fragment it is difficult to draw any conclusions about the entire colony. 

 The coenoecium is yellowish white. It may perhaps be thought that the pale colour is 

 due to disintegration after the zooids had died or left the colony ; but the experiment of 

 Ridewood (1918 a, p. 60) refutes this. In order to test the durability of the coenoecium 

 he kept a piece of colony in distilled water partly exposed to air. At the end of two years 

 there was no difference between this piece and the remainder, preserved in alcohol. The 

 pale colour of the coenoecium is therefore the natural colour of the entire colony. Short 

 lateral branches with ostia are borne along the sides. The ostia are like those of Forms 

 A and B. Each short branch has three or more ostia which may be divided. The edges 

 of the ostia bear four or more spines which are sometimes forked. The spines are not 

 more than 1-5 cm. long and are blunt. 



The internal anatomy of the zooids is treated in a separate section. Points of systematic 

 importance are given here. A fairly extended zooid measures from 2-2 to 3-2 mm., and 

 possesses ten or twelve arms. The stolon arises from the basal region of the body and 

 carries two or four buds. The length of the stolon depends on the amount of contraction 

 at the time of death. A fairly extended one measures up to 6 mm. Very often the zooids 

 are found crowded together into certain parts of the cavity, and the stolons and buds 

 are entangled in such a way that they cannot be easily separated. 



The colour of the zooids and the number of arms present an important problem which 

 has not been properly studied until now. Andersson (1907) stated that in C. inaequatiis 

 the males have twelve arms and females ten. But from the collections of the ' Terra Nova ' 

 Expedition Ridewood (1918 a, p. 64) showed that there is no great correlation between 

 number of arms and sex. One difiiculty of verifying this result is that in most zooids 

 the gonads are immature so that their sex cannot be determined. 



In the present collection I was able to distinguish : (a) colonies in which all the zooids 

 are crimson-brown and bear six pairs of arms, (b) colonies in which all the zooids are 

 pale brown and possess ten or occasionally eleven arms, (c) colonies in which both kinds 

 of zooids are present, though the crimson-brown ones predominate. Sections of these 

 two kinds show that the crimson-brown zooids are always females with well-developed 

 paired ovaries, and that the pale brown zooids are males. Therefore some of the colonies 

 are unisexual and others bisexual, although in these female zooids are the more numerous. 



