GIGANTOCYPRIS MULLERI 207 



the other end of the lateral brace there is a thin sclerite e, which slopes downwards 

 and backwards and markedly inwards (Fig. 6) to an L-shaped groove in the body wall 

 in which lies the beginning of the second trunk limb (Figs. 4-6). In the anterior wall 

 of this groove the e sclerite divides into two branches, one running upwards and the 

 other at right angles running forwards. 



I have called this system the articulated sclerite system because in Doloria the abc 

 sclerite was certainly an articulated series of three separate sclerites. In Gigantocypris 

 I am using the same name, but, as I have remarked, I cannot find any real articulation 

 between the sclerites except in the minor case of the small d sclerites supporting the 

 antenna. The sclerites, however, undoubtedly can be moved relative to each other as 

 the muscular system demonstrates, but this must be through the flexibility of the 

 system rather than its articulation. The skeletal rods in Gigantocypris are, relative to 

 the animal, much more slender than those of the smaller form, Doloria, so that while 

 in the latter articulations were necessary, in the giant form such movement can be 

 brought about merely by the bending of one part or another. 



It may be suggested that in such an enormous body as that of Gigantocypris any 

 flexibility of the skeletal rods would render them too unstable to support any muscular 

 movement. But the sclerite system is a series of rods in a very thin flexible bodv wall. 

 The contraction of the dorsal muscular system which I have described produces con- 

 tinuously a high internal body pressure which will put this thin body wall in a state of 

 tension. This will tend to restore any deformation of the narrow sclerites due to 

 muscular activity, and so must render the sclerite system stable. 



In Fig. 5 I have drawn the right sagittal half of Gigantocypris showing the sclerite 

 system, and have inserted those muscles which are connected with it and with the 

 adductor tendon. 



The muscle numbered 1 is not strictly attached to the sclerite system. It runs from 

 the lower median part of the nauplius eye to attach direct to the shell just below and 

 lateral to the pericardium. It is one of a group of three parallel muscles whose position 

 of upper attachment can be seen in Fig. ya and Plate XXXIX, fig. 2. Of the other two, 

 no. 2 is attached ventrally to the confluence of the c sclerites, just behind the antennules. 

 No. 3 appears to slip under the b sclerite. It is, however, attached to the sclerite and at the 

 same time to the lower margin of the vestigial paired eye. These three muscles must have 

 a direct effect of raising the sclerite system and hence the whole front part of the body. 



In isolated preparations muscle 3, the b sclerite, and the vestigial paired eye always 

 remain firmly connected together. This muscle corresponds to the large postero-dorsal 

 eye muscle that I describe but do not figure in Doloria (193 1, p. 451). With the 

 degeneration of the paired eyes in Gigantocypris the muscle has not disappeared ; it has 

 become relatively smaller and changed its function — instead of running under the b 

 sclerite as a pulley it attaches to it and so assists the other muscles in lifting the anterior 

 part of the body. The vestigial paired eyes are probably capable of being moved only 

 as the sclerite system is moved for the other paired eye muscle — the anterior eye 

 muscle — has disappeared. 



