ON THE ANATOMY OF 

 GIGANTOCYPRIS MULLERI 



By H. Graham Cannon, Sc.D., F.R.S. 



Beyer Professor of Zoology in the Victoria University of Manchester 



(Plates XXXIX-XLII; Text-figs 1-17) 

 INTRODUCTION 



The following account of the internal anatomy of the giant deep sea Ostracod 

 Gigantocypris was undertaken originally with the intention of discovering what 

 modification in the anatomy of a typical Cypridinid had taken place in the evolution 

 of this relatively enormous form. I took the view that the small Ostracod such as 

 Doloria, whose anatomy I had previously described (1931), represented a more primitive 

 constitution from which that of Gigantocypris might have evolved and not the reverse — 

 a view put forward by Liiders (1909). I have previously stated my reasons for adopting 

 the view that the primitive crustacean was a minute form (1933) and the same argument 

 will apply to the ancestral Ostracod. 



The abundance of material, however, which was placed at my disposal and its excellent 

 state of preservation soon led to a much wider investigation, so that the present paper 

 in addition adds considerably to the description of Cypridinid anatomy which I pub- 

 lished for Doloria. 



Liiders (1909) gave a general account of the anatomy of Gigantocypris, and he dealt 

 with certain organs so thoroughly that I have omitted any particular account of them 

 in my own work. Thus the unique nauplius eye, which is a characteristic feature of the 

 genus, I have omitted except for brief references. In addition, as in Doloria, I have not 

 dealt with the genital organs or with the labral glands. Liiders has adequately dealt with 

 these systems. 



The sections for this work were cut and stained by the head laboratory steward, 

 J. T. Wadsworth, just before he retired after nearly forty years' service to the depart- 

 ment. I am grateful of this opportunity of expressing my thanks to him and appreciation 

 of all the useful influence he has exerted over so many zoologists during his long 

 stewardship. 



METHODS 



Three specimens received from the first commission of R.R.S. ' Discovery' had been 

 fixed in alcoholic Bouin. The smallest of these— about 1 cm. diameter— was cut at 10/t 

 in ordinary paraffin wax. The body collapsed considerably but was useful for a study of 

 certain organs, e.g. nerve ring and antennal gland. The others were dissected and isolated 

 pieces were embedded. The dissection, however, led to such distortion that they were 

 only of use for minute details, e.g. the constitution of the sphincter of the antennal gland. 



