148 Marine Investigations in South Africa. Vol. V. 



testes are not well developed, the seminal ducts not broad and con- 

 taining no spermatozoa. The immaturity of the female sexual 

 apparatus is recognised by the limited number and size of the ovaries, 

 as also by the poorly developed uteri and shell gland. 



The bursa copulatrix of the female copulatory apparatus is in the 

 form of a large strong muscular egg-shaped organ, the pointed end of 

 which is directed backwards. The inner surface of the bursa copu- 

 latrix is provided with rather large closely set papillse. The largest lie 

 in the centre of the organ, and they gradually diminish in size towards 

 the anterior and posterior regions. They are provided with a broad 

 basis and are partly drawn out into points and partly more or less 

 rounded off. The papillas are covered with an epithelium which is 

 a continuation of the ventral epithelium of the body, and this varies 

 in different parts of the bursa copulatrix ; at its distal end it is 

 extremely flat and its cells are only to be distinguished by their 

 nuclei. Nearer, on the larger papillae, it loses its nuclei, becomes 

 thickened and assumes the appearance of a strongly refractive chiti- 

 noid membrane, coloured an intense yellow with picric acid. In its 

 further course it again assumes the characteristics of a flat epithelium, 

 which becomes glandular in character at its anterior end. The 

 papillge in the bursa copulatrix probably serve in some sort of way 

 aa accessory organs of copulation. The anterior end of the bursa 

 copulatrix, which is provided with glandular epithelium, may be 

 regarded as the beginning of the duct of the shell gland, which runs 

 further forward. The shell glands occur in fewer numbers in the 

 epithelium of the duct ; in its neighbourhood, i.e., in the parenchyma, 

 there are however none present. The duct is continued forward to 

 the region of the male genital apparatus, here bending round in a 

 backward direction and passing into the oviduct. This is clothed 

 with a cubical epithelium ; at its commencement it includes a 

 common part of both uteri and is continued to a point over the 

 middle of the bursa copulatrix. The accessory vesicle is absent. 

 The uteri consist of narrow canals which do not contain any eggs 

 I was unable to follow them throughout their whole course. 



This animal belongs to the family of the Planoceridae, in which it 

 agrees most closely with the genus Planocera, group A, but it differs 

 considerably from other species of Planocera. The male copu- 

 latory apparatus is characterised by the abnormal structure of the 

 penis and the granule-gland. The difference of the female apparatus 

 from that in other species of this group consists in the peculiar 

 structure of the bursa copulatrix, which is provided with papillae, and 

 in the absence of the accessory vesicle. I have named this animal 

 Planocera Gilchristi in honour of its discoverer. 



