466 



different genera, families, and even orders. In this last conclusion, 

 which has an important hearing upon the question of the real value 

 and meaning of natural history species generally, Dr. Carpenter has 

 heen fullv borne out by the parallel inquiries of Messrs. Parker and 

 Rupert Jones, which, relating to an extensive series of less developed 

 types not especially studied by him, form, as it were, the complement 

 of his own. 



In his researches on the embryonic development of Pur pur a Lapil- 

 lus, Dr. Carpenter's attention was specially directed to the elucidation 

 of the fact, that, from the many hundreds of egg-like bodies contained 

 in each nidamental capsule, only about thirty embryos are evolved, 

 each of them many times larger than the ovum from which it origi- 

 nated. It had been affirmed by some previous observers that the 

 entire assemblage of ova coalesces into a single mass, which subse- 

 quently breaks up into a smaller number of portions, each of which 

 developes itself into an embryo. Dr. Carpenter, on the other hand, 

 was led to the conclusion, that of the total number of egg-like bodies, 

 a few develope themselves into embryos after the usual plan of 

 aquatic gasteropods, while the remainder coalesce into a single mass. 

 To this mass the embryos attach themselves by their mouths, and 

 gradually ingest the particles of which it is composed until it is all 

 shared among them ; they thus become distended to many times 

 their original bulk, and on the additional store of nutriment thus 

 obtained, their development is carried on to an advanced stage 

 within the capsule. Dr. Carpenter's account of the process was 

 warmly attacked by certain observers who had given a different ex- 

 planation of it, but it was fully confirmed by subsequent trustworthy 

 inquirers ; and there seems a strong probability that it is true of the 

 Pectinibranchiate Gasteropods generally, since in many of them the 

 like replacement of numerous small egg-like bodies by a few large 

 embryos has been observed. 



DR. CARPENTER, 



You have been long engaged in the cultivation of a science which, 

 important as it is in various other ways, has this peculiar interest, 

 that it leads us to a more exact knowledge than we could otherwise 

 obtain of that part of the creation to which we ourselves belong ; 

 not only explaining the structure and functions of the various organs 



