22 



what characteristic surface or shallow water fauna of 



minute forms. 



In St. Jerome's Creek the microscopic fauna of its head 

 waters is entirely different from that of the body of the 

 creek ; two minute forms inhabit in vast numbers the 

 former, while I sought in vain for them in the more open 

 and changeable waters of the main body of the inlet, 

 which are brought into active movement twice a day by 

 the action of the tides. One of these forms an Infuso- 

 rian^, l-25th of an inch in length, was found covering 

 every available surface of attachment, so that countless 

 multitudes of the naked young would be swimming 

 about in the water previous to building the curious spiral 

 tubes which they inhabit; admirably fitted in this state 

 as food for the oyster. Beside the type referred to there 

 were a number of other Infusorians which in their so- 

 called swarming stages of development, the young would 

 become available as oyster food. Of such types I noticed 

 four different species, either belonging or very nearly 

 related to the genus Cothurnia ; all of the forms built 

 tubes for themselves. I also noticed several forms of 

 bell-animalcules, the swarmers of which would become 

 available as food for the oysters lying in the vicinity. 



The diatoms did not seem to me to be more abundant 

 in the head waters than in the open creek. There was 

 one moss animal, of remarkable character, which I found 

 in the head waters only, this creature was very abun- 

 dant, and no doubt its embryos like those of the infuso- 

 ria referred to, were available as food. 



Of free swimming Infusorians, I noticed a number of 

 genera ; one especially attracted my attention from its 

 snake-like appearance and singularly rapid contortions ; 

 it had a tuft of vibrating hairs or cilia at the head end in 

 close relation with the mouth. Another more abundant 

 type was the curious genus Euplotes^ with a thick shell 

 enclosing the soft protoplasm of the body ; the latter 



*On the occurrence of /^r«a/r<7rf«c/a, Wright, in the Chesapeake Bay. Atn. Naturalist^ 

 1880, pp. 810 — II. 



