426 PROF. G. O. SARS ON 



24. Zoological Results of the Third Tanganyika Expedition, 

 conducted by Dr. W. A. Cunnington, 1904-1905. 

 Report on sorae.larval and young stages of Prawns from 

 Lake Tanganyika. By Prof. G. 0. Saes, C.M.Z.S. 



[Rsceived December 5, 1911 : Read March 5, 1912."] 



(Plates LVII.-LX.*) 



Introduction. 



In the tow-nettings taken by Dr. Cunnington during the Third 

 Tanganyika Expedition and placed in my hands for examination 

 of the Oopepoda and Ostracoda, some larval and young stages of 

 Prawns were also found. Having submitted these stages to a 

 closer examination, I find that some notes about them may be of 

 interest. We owe to Prof. E. von Daday a rather elaborate 

 account of the postembryonal development of Caridina niloiica, 

 var. gracili2)es (=C. loyckii de Man) from Lake Victoria Nyanza, 

 and I have also myself had occasion to examine some larvae 

 from that lake, occurring in the samples taken by Dr. Cunnington. 

 They agreed on the whole very well with the descriptions and 

 figures given by Prof. Daday. On the other hand, the larvte found 

 in the samples from Lake Tanganyika have proved to be rather 

 difierent, ajDparently owing to the fact that they belong to genera 

 quite different from Caridina. 



In the present paper I propose to describe thi-ee larval forms 

 and one young one, representing as many difierent stages of 

 development. Two of these forms undoubtedly represent very 

 early larval stages (so-called Zoese) ; but they differ conspicuously 

 both in size and in the development of the appendages, and 

 apparently belong to two quite different kinds of prawns. Of 

 course it is very difficult to decide with any claim of certainty 

 as to the species or even genera to which these larvae are 

 leferable ; but I believe that they are in themselves interesting 

 enough to merit a detailed description. They are here simply 

 recorded as Zoea Nos. 1 and 2, though some suggestions about 

 their probable origin will be set forth. The 3rd form is a larva 

 in the last, so-called Mysis stage ; and the 4th is a very young 

 prawn in the 1st postlarval stage. Both these forms admit of 

 being more certainly referred to a definite species. At the close 

 of this paper some general remarks will be given. 



Zoea No. 1. (PI. LYII.) 



This larva undoubtedly represents the very first postembryonal 

 stage of some Tanganyika Prawn, having apparently just been 

 hatched. It is remarkable for its small size and the very simple 

 structure of the appendages, being indeed the most primitive 



* For explanation of the Plates see pp. •1'39-J:10. 



