7<32 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. [8] 



and proven in some cases to be at least the vehicles of infection in cer- 

 tain diseases. These organisms, which are very minute, are the first 

 to appear in disintegrating or i)atrefying organic infusions. If small 

 Protozoans, such as Paramceciiim, are left to die in improperly aerated 

 water, or water otherwise hurtful to them, they are, under favorable con- 

 ditions, immediately attacked by these Microhia,* which then 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 organ- 

 isms, 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 the direction of the throat, 

 the lower end of which is dilated into a globular space by the force of 

 the currents produced by the cilia, in which the particles of food are 

 rotating in the contained water. This space enlarges gradually until 

 eventually its connection with the throat is suddenly broken by a col- 

 lapse of the walls which join the globular space with the former. In 

 this way food-vesicle after food-vesicle is taken into the body of the 

 animalcule, from which the creature will abstract whatever is useful 

 and cast out near the mouth whatever is contained in the food-vesicles 

 that is indigestible. The writer has seen the process in a number of 

 forms, and it is not unusual to observe a dozen or more food-vesicles in. 

 the body of a single Protozoan. Many parasitic forms, however, are 

 mouthless, such as Ojjalina, Benedenia, Pyrsonympha, Trichonympha, etc., 

 where the nourishment is probably obtained from their hosts by transu- 

 dation through the body-walls. In other forms again comparatively 

 large objects are swallowed with apparent ease, judging from shells of 

 other x)rotozoan types which are found within their bodies. Such a 

 form I encountered in a slightly brackish water pool near New Point 

 Comfort, Virginia, during the summer of 1880. It was apparently a 

 very large species of Prorodon of an irregular cylindrical form which 

 had in a number of instances swallowed five or six large Difilugians, 

 Arcella vulgaris, the shells of which remained within the animal to tes- 

 tify to the nature of the food it had been devouring. Some other mbde 

 of swallowing such large prey is probably practiced by this large ciliate, 

 very diflerent from the method first described. In the same pool a very 



* Ov ScUzomycelcs, tbo germs of which are abundant in the surrounding air, and 

 from which the infection in such cases is derived. In some eases it may be observed 

 that the body of the dead Protozoan is attacked at one side, which becomes the cen- 

 ter of multiplication, from whence the putrefactive organism multiples by germina- 

 tion, gradually invading and appropriating the dead protoplasm of the organism 

 upon which it feeds. These forms seem to have little or no power of forming living 

 matter de novo from ammonia, carbonic dioxide, and water, but, like animals, appropri- 

 ate pre-existing living matter, or such as has ceased to manifest vital phenomena. 



