228 RAMBLES OF A NATURALIST. 



nected with some of the most intricate points of 

 zoology, being based upon the study of artificial 

 fecundation. Here, however, it will be necessary 

 to enter into a few preliminary and explanatory 

 details. 



After they have attained the adult state, the Te- 

 redos live secluded within their galleries, which 

 being lined with a calcareous matter secreted by 

 the animal itself, have no communication with one 

 another. This circumstance led to the Teredo being 

 classed among those animals which are at the same 

 time male and female ; but although this opinion has 

 been generally admitted it is not founded on fact. 

 Here, as in many other cases, nature has solved the 

 problem proposed to her in a manner wholly at 

 variance with our preconceived ideas. Notwith- 

 standing the cenobite life which the Teredos lead 

 they are of distinct sexes. At an epoch which 

 varies according to the species*, the females emit 

 their eggs, which are arrested within the folds of the 

 respiratory organs. Within this singular nest the 

 young animals are born and live for a certain length of 

 time under a very different form from that which they 

 subsequently acquire. f At the moment when they 



* It was long believed, and seems still to be the opinion of some 

 naturalists, that our seas only possess one species of the Teredo. 

 This, however, is evidently an error. At Pasages, I found two 

 perfectly distinct species. The one kind ceased depositing its ova 

 towards the end of October, after which time all the larvae which I 

 found in the branchiae were already living and capable of indepen- 

 dent motion. The other probably lays its eggs in the spring. 



j This kind of incubation is common to many other Acephalous 

 Molluscs. The Anodonta and other fresh-water Mussels may serve 



