584 



DR. W. A. CUNNINGTON ON THE 



recorded from the same locality as S. sfuhlmanni. Nothing 

 further is known of this form. 



Examples of two spscies of Stenostoma from Bukoba were 

 among the material examined by Bohmig, but their unfavourable 

 state of preservation did not permit of nearer identification. 



5. Gyrator hermaphroclitus. 



A pelagic Turbellarian collected in Victoria Nyanza is identified 

 with this species by Bohmig. It is well known in Europe. 



6. Vor^tex quadridens. 



This type is established merely on the evidence of sketches and 

 notes by 8tuhlmann. It is admitted that certain important 

 features of the genital apparatus are unknown. Obtained from 

 stagnant water at Bukoba, 



From the above it will be observed that Turbellaria are only 

 recorded at present from Lakes Victoria and Tanganyika. From 

 Victoria Nyanza and its neighbourhood five forms have been 

 specifically identified, three of them being peculiar to the lake. 

 There are, in addition, two types which are unnamed. These 

 records of Bohmig, however, need confirmation, as they are based 

 on very meagre evidence. From Tanganyika a single endemic 

 species is known, which belongs to the widely distributed genus 

 Pkm:iria *. No doubt further representatives of this group will 

 eventually be found in the great lakes, but they appear to be less 

 common than might have been expected. There is no suggestion 

 of a striking Turbellarian fauna in Tanganyika and little indica- 

 tion that such will be discovered in the future. 



Trematoda. 



Practically nothing is known of the distribution of these 

 exclusiv^ely parasitic animals in the lakes of Africa. Following 

 the argument advanced in the section dealing with the Nematoda, 

 it seems only logical to include such forms in a lake fauna. In 

 the case of these organisms they may be obtained in the free- 

 swimming larval stage, or infesting an intermediate Molluscan 

 host or in their final vertebrate host. As far as I am aware, the 

 description given by Daday (76, p. 39) of two Cercaria larvae from 

 the neighbourhood of Nyasa is the only account which concerns 

 any of the lakes. Both were found in material from ponds near 

 Nyasa and were described as new larvae, though it seems doubtful 

 whether such determinations have much systematic value. They 

 have received the names of " Cercaria'' SGhizocerca and Gercaria^^ 

 hoplophora 76, p. 288). 



* It clear that Stuhlinann's statement that Planaviaus cannot survive 



temperatures of over 25° C. (185, p. 3i9) is uot universally true. The specimens I 

 collected in Tanganyika were taken in quite shallow water, where the temperature 

 toiuls t') hs highest, yet my thermosneter readings for the surface of the lake showed 

 a higher average than 25°. 



