REPORT ON THE PTEROPODA. 
3 
because he had opposed to him the dogmatic views of Cuvier, which were then all- 
powerful. Recently, however, the authors above mentioned have returned to an opinion 
closely resembling that of de Blainville ; but in order to place this upon a firm basis, 
further demonstration is still necessary. 
On these grounds I have proposed to make the present Report a comparative 
anatomical study of these animals rather than a descriptive anatomical monograph, and 
shall attempt mainly to throw light upon then systematic position ; and by the per- 
mission of Mr. John Murray to conclude this third part of my Report upon the Pteropoda 
by an exposition of my views regarding their relations to the other groups of Mollusca. 
Having thus defined the object of the present work and the spirit in which it is 
conceived, I may say a few words regarding the method which has been followed in its 
elaboration and the manner in which I have divided it. 
The first portion of this Report bears upon the descriptive anatomy of the Pteropoda, 
taken genus by genus, treating first of the Thecosomata, then of the Gymnosomata. As I 
have indicated above, no attempt will here be made to discuss the whole organisation of 
each genus, but I shall study especially — 
1. The points neglected or misinterpreted by previous authors, in order, if possible, 
to elucidate them. 
2. The points which seem to me to have an important bearing upon the relations and 
systematic position of the Pteropoda. 
In this portion I shall not attack the question of the embryonic development of the 
Pteropoda. Too few embryos were collected by the Challenger to furnish any new facts 
which might serve as a basis for a discussion of this special subject. The histology of the 
Pteropoda, too, will only occupy an unimportant place in our discussion, for the specimens 
collected by the Challenger were not preserved with a view to histological examination. 
Hence, in order to fill up the numerous lacunse which will occur in the present work, I 
hope to publish hereafter the results of my examination of fresh specimens at the Naples 
Zoological Station. 
In the second part it is proposed to study the relations and affinities of the group of 
Mollusca called Pteropoda by a comparison of their organisation (as ascertained by the 
investigation described in the first part) with that of other Mollusca. 
