SPLEEN OF LEPIDOSIREN AND PROTOPTERUS. 231 
The Early Development of the Spleen of Lepido- 
siren and Protopterus 
By 
Cl. L. Purser, B.A., 
(Sometime Coutts-Trotter Student, Trinity College, Cambridge.) 
With Plates 15, 16, and 17. 
My first words must be those of thanks to Professor Graham 
Kerr for providing me with every facility for carrying out 
the research, the results of which are embodied in this short 
paper. He invited me to work in his laboratory, provided me 
with material already stained and mounted, and was especially 
helpful in suggestion and criticism. 
Owing to the uncertainty as to the time available for this 
work, I have done no fresh section-cutting, nor have I re- 
stained any of the sections already made. This being so, I 
found that the earlier stages of Protopterus were more suit- 
able for the present investigation than those of Lepido siren, 
and so I will first describe its development in detail, and then 
contrast and compare that of Lepido siren, adding further 
details where I can. 
The Spleen of Protopterus. 
In the earlier stages than N.T.XXXII . 1 the foregut is short, 
thick, and solid, its enveloping mesoderm being yolky, and 
with difficulty distinguishable from the subjacent endoderm. 
1 The stages are designated by the numbers used in Keibel’s 
Normentafeln.’ 
