METAMORPHOSIS OF CRUSTACEA. 455 



in the harbour of Cove during the Spring months ; by this 

 discovery its identity, through Slabber's rude figure, became 

 sufficiently apparent. 



Some important results and reflections naturally present 

 themselves from a consideration of the foregoing detail, but 

 they derive a ten-fold degree of interest by the subsequent 

 discovery of the metamorphosis in the pedunculated Cirripedes, 

 as developed in the Memoir read before the Royal Society. 

 Without this we should still remain ignorant of the real 

 affinities of this curious parasite, and of the mystery of its 

 procreation. That it agrees with no tribe of the Crustacea 

 is apparent, not even with the Cirripedes; nevertheless, its 

 concealed affinity to these latter becomes evident, on a com- 

 parison of the respective larvae; and yet how different and 

 masked is the perfect animal, which presents us with another 

 point of affinity in a union of the two sexes in the same 

 individual ; indeed, the Sacculina furnishes the only example 

 in nature of an animal all generative organs, to the apparent 

 exclusion of every other, — its body being entirely filled with 

 the ovaria, and an enormous testicular gland. (Fig. 3.) 



Fig. 3. 



To an animal permanently fixed, and deriving its sustenance 

 wholly through the medium of another, sight and members 

 would have been useless, and are therefore cancelled by a 

 Providence which never errs, and invariably adapts every 

 animal to the peculiar station it is intended to fill in the scale 

 of existence. In this respect it is however singular, as there 

 are no other parasites of this class but retain some few mem- 

 bers, if only for the purpose of adhesion. 



If any naturalist is disposed to dispute the claim of Sacculina 

 to the rank of an animal when in its last stage, and to consider 

 it as a mere conceptacle, I have only to observe, that its long- 

 continued growth, and the complication of an obvious testicular 



