1885.] NEW-YORK MICROSCOPICAL SOCIETY. 69 



ing his tail behind him, which, of course, was the proper place, 

 if he must carry it at all. Now it was just this " at all " which 

 perplexed me. The books said that the tadpole's tail is lost by 

 atrophy — that is, that it dries off. Nonsense ! Nature does not 

 entail such a waste of the raw material. I watched the frog day 

 by day, and discovered that the caudal annex was being absorbed. 

 It was getting shorter, but the shortening was going on at the 

 thick, or proximal end. Now, so it was — every particle of that 

 appendage was taken in. This done, the animal had to forage 

 for subsistence. And similarly is it with our baby oyster while 

 laying the foundation, and shaping its house. That prominent 

 organ, the swimming pad, is getting absorbed — for it is now its 

 food-supply. It is now developing internally, for as yet there is but 

 little more than the beginning of things. The intestine is simply 

 a short, straight organ, and is not yet convolute. But the liver 

 is very large ; in fact, it quite preponderates. 



And what of Ostrea's life ? Who are her friends ? There is a 

 pretty red branching sponge, which often grows upon the oyster, 

 Microciona proUfera. Formerly it was very common. It is less 

 so now. This sponge often serves the oyster well, in buoying 

 the bivalve up when sinking in the mud. It is also in its way a 

 grove in which the infusoria breed, and so supply food to the 

 mollusk. The oyster, too, has a gay "commensal." I like this 

 pretty old word of Chaucer, meaning one who dines at our table, 

 and is welcome there. Of course, all this precludes the idea of 

 a parasite. This gay little commensal is a red and white crab 

 hardly larger than a pea. It lives literally in the oyster, en- 

 sconced between the folds of the mantle — but it does not live 

 upon its host. Between them both there seems to be a good 

 understanding. It is the female Pinnotheres ostreum. Experi- 

 enced oystermen have told me that it is rarely found except 

 with oysters in good condition. The curious fact is that it is 

 only the female Pifinotheres that lives in the oyster. The male 

 is often seen floating on the surface of the water, with a pretty 

 white anchor on his jacket, the gay little sailor that he is. His 

 general hue is brown. He has a harder shell than the female, 

 whose shell is thin and transparent. The truth is that, though 

 twice as large as the male, she is very tender, and her coddling 

 life as a commensal, is a necessity. The red sponge I have men- 

 tioned is called by the oystermen " red-beard." There is another 



