242 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



zooids to the superficial square iucli of frond surface. At this rate 

 there would be 39,204,000 zooids found to populate a single square rod 

 of frond surface. Estimating the number at only 100 per square inch, 

 which is low, and which would, I think, represent a fair average over 

 considerable areas where the conditions of life were favorable, there 

 would still be a stalked protozoan population of nearly four millions to 

 the square rod. The most abundant of these compound forms was one 

 which very much resembles Zoothamnium alternans, Glaperede, found on 

 the west coast of Norway. The same form was again found in vast 

 abundance upon algsB in Cherrystone Eiver, near the mouth of the 

 Chesapeake, during the season of 1881. Upon one occasion I found it 

 in great abundance growing on all parts of the body of a Finnotlieres 

 which was living in the gill-cavity of an oyster, its swarmers, or young, 

 as they were thrown off, in all probability forming part of the food sup- 

 ply of the mollusk. 



I have been interested upon several occasions to observe that the very 

 minute stalked collared monads, Salpingceca Rud Oodos w/a, are frequently 

 to be found attached to the stems of the compound colonies of bell-ani- 

 malcules, or gathered about in the vicinity of the point of attachment 

 of a single one. In such cases the monads appear to derive a benefit 

 from the currents or vortices set uj) in the water by the waving of the 

 ciliary crowns of their giant neighbors, which bring particles of food to 

 their very doors as it were. On one occasion I found individuals of a 

 species of Vorticella fixed to the egg-membrane of the ova of the cod- 

 fish at Wood's Holl, Massachusetts, as had been previously observed by 

 E. E. Earll, and in their vicinity were several colonies of a compound 

 stalked monad, resembling the Dinohryon of Ehrenberg. On another 

 occasion I found something like Poteriodendron on the Zoothamnium 

 which covered a Pinnotheres inhabiting an oyster; but the chain of par- 

 asitism did not stop here, for on the monad, as well as on the bell-animal, 

 there were rod-like bodies attached which were presumably bacteroid, 

 as has been supposed by Stein. Stalked monads are probably much 

 more common than has been supi)osed, which reminds me that I have 

 detected the occurrence of PMpidodendron splendidmn in the bogs and 

 ponds of New Jersey, a form which was described originally by Stein 

 from Bohemia. Minute as the stalked monads are, they must Uve on 

 still minuter beings, probably upon the Microbia, which in their turn 

 become an indirect source of supply of food for the grades next above 

 them, such as the free and fixed ciliate Protozoa, which feed upon monads 

 which have themselves fed on Bacteria or Bacillus-like organisms, and 

 so onward the matter of life takes its upward way. 



The process of swallowing of many ciliate infusorians is as peculiar 

 as it is interesting. An opening, oftenest at one side of the body, is the 

 mouth, from which a short blind canal passes into the soft substance of 

 the animal's body. The rapid vibration of rows of cilia in the vicinity 

 of the mouth creates currents which set in in the direction of the throat, 



