DEVELOPMENT OF FAT-BODIES IN BAN A TEMPORAEIA. 141 
II. The part of the kidney which undergoes this con- 
version into fat-body is the pronephros or head-kidney. 
III. It seems very probable from analogy, and from the 
researches of Rosenberg, that the structure in front of the 
true kidney in Ganoids and Teleostei, described by Balfour as 
lymphatic tissue, is the persistent but structurally and func- 
tionally modified pronephros. 
1Y. The fact that a part of the kidney undergoes such 
a remarkable change, the rest remaining normal and func- 
tional, is an additional argument in support of the view that 
the pronephros has a different phylogenetic history from the 
mesonephros, and that it is more ancestral. 
It only remains for me to perform the pleasant duty of 
expressing my warm thanks to Professor A. Milnes Marshall 
for the uniform and stimulating kindness with which he has 
helped me iu this short research by suggestions and criticisms ; 
he has been good enough to go over my specimens with me, 
and to discuss with me my results. 
I desire also to express my obligations to my friend Dr. 
G. Herbert Fowler for much valuable and practical assistance. 
My thanks are further due to Professor Stirling, under 
whose direction the work has been done. 
