544 R. T. GUNTHER. 



In his original paper Professor Ray Lankester drew attention 

 to the unique nature of this peculiar organ, and pointed out its 

 relation to the endoderraal sense-organs of other craspedote 

 medusae, such as the Trachomedusae. 



The interest attaching to this organ is now all the greater 

 because another medusa (Limnocnida tanganjicse) has 

 been discovered with similar and similarly situated sense- 

 organs, of which the axial cells are also endodermal. The 

 new medusa, moreover, is also an inhabitant of fresh water. 

 In Limnocnida the organ is identical in every important 

 respect, the chief diflFerences being that the sacs are not pro- 

 longed into the velum, and that the refringent bulbs, as a 

 rule, consist of fewer cells, but in both Limnocodium and 

 Limnocnida no otolithic concretion is formed. 



Endoderm. — The endoderm of the gastric cavity has 

 already been the object of a very thorough investigation by 

 Professor Ray Lankester in his paper on the " Intra-cellular 

 Digestion of Limnocodium" (3). Proceeding from the mouth 

 towards the stomach, three regions have been distinguished 

 by Professor Lankester, all differing in regard to the nature 

 of their epithelial lining. The endoderm of the first region 

 nearest the mouth is composed of more or less granular cubical 

 cells, the nuclei of which are situated near the bases of the 

 cells (PI. 40, fig. 9). The epithelium of the second region 

 (fig. 10) is very much higher ; the cells composing it are pos- 

 sibly ciliated, though no cilia could be observed in the preserved 

 material. The nucleus is situated near the middle of the cell, 

 and separates the protoplasm of the inner half, which is fairly 

 clear, from the very granular protoplasm of the outer half. 

 The epithelium lining the third region (fig. 11) or stomach 

 proper is composed of very large cells, and it is in this region 

 that intra-cellular digestion occurs. Among the large vacuo- 

 lated digestive cells are numerous goblet gland-cells, and here 

 and there a fragment of food may be seen which is undergoing 

 intra-cellular digestion, as in PI. 40, fig. 11, x. 



Fig. 12 illustrates the very abrupt transition between the 

 large-celled digestive epithelium of the third region and the 



