310 ORDER FLAGELLATA-PANTOSTOMATA. 



of the Royal Society' for May 1878, as a "minute septic organism," no technical 

 name being given nor any attempt being made to identify it with any previously 

 described form. It being the only type, among the many so painstakingly in- 

 vestigated by Mr. Dallinger, in company usually with Dr. Drysdale, that repre- 

 sents both a new generic and specific form, the author derives much pleasure from 

 bestowing upon it technical titles that shall serve to perpetuate their names in 

 connection with this group of organisms. 



As in the case of the numerous other monadiform beings referred to in this 

 volume which have formed the subject of that authority's investigations, the entire 

 life-cycle, as hereafter related, has been traced out. So far as can be at present 

 determined, this special type would appear to exhibit a close affinity with the repre- 

 sentatives of the genus ffeteromita, from which, however, it is at once distinguished 

 by the presence of two lateral instead of a single ventral anchoring filament. No 

 reference being made to the existence of a distinct oral aperture or the presence of 

 incepted food-granules, it must be provisionally assumed that the animalcule feeds 

 by endosmosis, after the manner of the Opalinidse, upon the nutritive fluids in 

 which it takes up its residence. 



Dallingeria Drysdali, S. K. PL. XIX. FIGS. 35-41. 



Body elongate-ovate, about three times as long as broad, widest and 

 rounded posteriorly, constricted centrally, the anterior region abruptly 

 narrowed and neck-like; flagella subequal, long and slender, about twice 

 the length of the body, the two lateral ones produced on each side 

 immediately behind the narrower neck-like region ; endoplast posteriorly 

 located. Length of body 1-4000". HAB. Animal macerations. 



The life-history of this species, as traced by the Rev. W. H. Dallinger, accords 

 broadly with that of Monas Dallingeri, Heteromita rostrata, and other flagellate 

 types upon which he and Dr. Drysdale conjointly have so successfully concentrated 

 their attention. Multiplication by fission represents the normal and most common 

 mode of increase. This process is preceded in the first instance by the splitting of the 

 anterior flagellum (see Plate XIX. Fig. 37), the line of segmentation extending thence 

 through the longitudinal axis of the body, including the subdivision of the endoplast, the 

 missing lateral filament being reproduced by the attenuation of the sarcode film which 

 lastly unites the eventually separated bodies. A period of from four to seven minutes 

 is occupied in the completion of this act of fission, which may be repeated at intervals 

 of three minutes for the duration of an hour. During the next two hours the same 

 process proceeds at intervals of from seven to ten minutes, while after this, fission is 

 more rare and sluggish and interrupted by irregular intervals varying from twenty to 

 as much as forty minutes. The phenomenon of longitudinal fission may, in this 

 manner, be continued, commencing with a newly developed individual, for a space 

 of from five to seven hours, when death most usually ensues. Much more rarely, on 

 an average of three cases out of nine, however, it was found that the monads at the 

 end of about three hours of continuation of this cleavage process, underwent a com- 

 plete metamorphosis. In these instances the two lateral flagella contracting, first 

 assume a knotted or clubbed aspect, and the body, losing its normal ovoid form, 

 becomes irregularly lobate around the margin and semi-amoeboid. The two lateral 

 flagella are ultimately entirely withdrawn, and the body, assuming a still more regu- 

 larly ovate contour than it originally presented, being without the central constriction, 

 progresses through the water as a simple monoflagellate organism, in all ways 

 identical with the ordinary representatives of the genus Monas. The endoplast 

 meanwhile increases largely in its proportions, and occupies a more posterior location, 

 while, in addition, a belt-like granular zone makes its appearance, encircling the exact 

 centre of the body, as shown at PI. XIX. Fig. 38. 



