104 METAMOKPHOSES OF MAN 



CHAPTER XI. 



METAMORPHOSES OF GASTROPODOUS AND ACEPHALOUS 

 MOLLUSKS. 



The discovery of metamorphoses among mollusks is 

 quite a modern one, and there are doubtless very many 

 more discoveries to be made in this branch of science. 

 In the year 1832, the celebrated German anatomist 

 Carus described for the first time the larvae of Ana- 

 donta, a sort of fresh-water mussel, which is abundant 

 in all the canals and ponds throughout Europe.* But 

 as always occurs in such cases, the facts, being quite 

 unexpected, were at first denied. It was asserted 

 that the larvae were only parasites, which existed in 

 great numbers in the gills of mollusks. They were 

 given a distinct name, and this erroneous interpre- 

 tation having had the authority of Carus's opponents 

 Rathke and Jacobson, became generally accepted. 



At this period, whilst modestly pursuing the practice 

 of medicine, and having, if anything, too much time 

 upon my hands, I devoted myself to natural history 

 when waiting for patients. In ignorance of the labours 

 of my distinguished contemporaries, I pursued the 

 same subject. I watched the development of the 

 anadonta's eggs daily, during at least five months, 

 from the time they were deposited, until an accident 



* Carus's memoir appeared in the " Nova Acta Naturae Curio- 

 sorum." 



