270 ]\Ir. R. T. Giinthcr on the 



rated to the ' Gescllscliaft iiatuvforscliondcr Freundc zii 

 Bdlin ' the substance of a letter iVoin Dr. K. Biihni, tlieii 

 travcllinc; in Africa, rohitiiiu; to the discovery of a Craspe- 

 dote Medusa in Lake Tanganyika. Tlic information to be 

 gathered from Bohm's account was restricted to the following 

 points : — that the Medusa was ]irovided with a velum ; that 

 it had a small short broad stomach, at the base of whicli the 

 genital organs are situated ; and, finally, that the tentacles 

 were very numerous and of unequal length. On account of 

 the complete ]ihysical isolation of Lake Tanganyika from all 

 other localities from which Medusai are known, Bohm very 

 justly considered the newly discovered species to be uidvuown 

 to science, and accordingly proposed the specific name of 

 ianffdiijicce, leaving the generic name, and at the same time 

 deploring that the absence of all necessary literature ])revented 

 him from further determining the zoological position of the 

 species. 



Evidently the same animal has since been observed by 

 H. von Wissmann, who, when describing his passage 

 across the lake on the 13th of April, 1887*, says, " I was 

 greatly astonished to observe a number of sea-nettles surround 

 our boat for about half an hour. Tiiey were transparent, 

 of the shape of a disk, and like a mark-j)iece in size; round 

 tlie edge was a milky circle, hanging down in fibres, by 

 means of which they swam." 



Such, then, are the sole facts which, so far as I know, have 

 been hitherto published concerning what is probably the most 

 aberrant of the very few freshwater Medusai at present known 

 to us. 



The specimens were preserved in strong alcohol and were 

 much blackened by the osmic acid which had been employed 

 as a fixing agent, and which had acted especially upon the 

 margin of the umbrella and the manubrium. In size the 

 individuals varied from 1 to 1*8 centimetre across the bell, 

 while the largest specimen was as much as 2*2 centim. in 

 diameter. 



The umbrella is characterized by its flattened shape, the 

 diameter being about four times as large as the greatest 

 thickness. The central portion of the umbrella, measuring 

 about two thirds of the whole diameter, is much thickened and 

 has the shape of a nearly hemispherical lens (PI. XIV. fig. 4), 

 while the jjeripheral jjortions are very much thinner. The 

 margin of the umbrella is bent over and incurved towards the 

 mouth. The exumbrella is smooth and covered with an epithe- 



• H. von Wissmann, ' Tlirou^rli Equatoiial Africa' (Knglisli transla- 

 tion), p. 2r,3. 



