GENUS HETEROMITA. 291 



in Heteromita correspond with those of Oikomonas, Amphimonas, Physomonas, and 

 other Flagellata previously described, as manifested by the capacity to incept food at 

 any portion of the periphery. Both Anisonema and Heteronema in this respect 

 offer a much more highly advanced structural type, each of these possessing, as 

 demonstrated by Biitschli and Stein, a distinct oral aperture and pharyngeal tract. 



In Stein's recently published volume several species of Heteromita are referred 

 to the genus Bodo ; the last-named generic title, however, does not adapt itself to the 

 forms included under the same denomination in this treatise, or as comprehended 

 in it by other recent authorities. 



The presumed resemblance between certain members of this genus and the so- 

 called zoospores of the parasitic fungus Peronospora infestans will be found discussed 

 in connection with the descriptive account of Heteromita lens, 



Heteromita lens, Mviller sp. PL. XV. FIGS. 1-17. 



Body exceedingly soft and plastic, susceptible of considerable alteration 

 of contour, usually subglobose, peach-shaped, or more or less ovate with a 

 slightly narrower anterior extremity ; flagella equal in size, very slender 

 and flexible throughout, about twice the length of the body ; endoplast 

 spherical, subcentral ; contractile vesicle posteriorly situated. Length 

 1-5000" to 1-3250". 



HAB. Vegetable infusions in both fresh and salt water. 



This species, here identified with the Monas lens of Miiller, occurs in vast 

 abundance in hay infusions in both fresh and salt water, being usually, indeed, the 

 first form to make its appearance in such artificial macerations. By continued and 

 repeated examinations, the life-cycle and developmental manifestations of this type 

 have been successfully traced, and are found to correspond broadly with those of 

 the two species studied by Messrs. Dallinger and Drysdale, next described. 



The results of the author's recent investigation of this form may be thus briefly 

 summarized : So soon as within twelve hours after placing the hay to macerate, the 

 ordinary spring water used had become slightly discoloured, and on examination was 

 found to contain, in addition to Bacteria, numerous excessively minute monadiform 

 beings, spherical in shape, measuring the i-2o,oooth part of an inch only in their 

 diameter. These minute organisms, as shown at PI. XV. Figs. 11-14, occurred 

 singly or united in groups or short moniliform clusters, and propelled themselves 

 through the water with an oscillating motion by the means of single, anteriorly 

 developed, vibratile flagella. These motile organs necessarily required the most 

 careful adjustment of the illuminating agency for their detection, and were often 

 made manifest only by the movements of the particles in the surrounding water 

 induced by their vibrations. At this early stage of their growth the monadiform 

 units might, in their isolated condition, be identified with the Monas punctum or 

 pulvisculus of Ehrenberg, or with any other of the simple globular forms of the 

 genus Monas, that are so minute as to have received at the hands of their first 

 discoverers no more definite description than that of mere moving points. The 

 moniliform or aggregated clusters, on the other hand, delineated at Figs, n, 12, 

 and 14, so essentially and unmistakably correspond with the younger and more 

 minute conditions of Monas lens, as depicted by O. F. Miiller in Table i. fig. 1 1 of 

 his ' Animalcula Infusoria' (1786), that the author has not the slightest hesitation in 

 identifying them with his species. A closer investigation of fragments of the hay 

 undergoing maceration revealed the presence of crowds of minute quiescent 

 sporiform bodies identical in size with the motile units, and as which they were later 

 on seen to detach themselves and swim away. These quiescent spores were found 

 scattered more or less thickly over the entire surface of the hay, and were in many 

 instances massed together in small symmetrical spheroidal heaps. The growth 

 in the maceration of the motile monadiform units just described, proceeded so rapidly 



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