294 ORDER FLAGELLATA-PANTOSTOMATA. 



angles, liberated countless spores of infinitesimal dimensions. A space of ten hours 

 was occupied in the attainment by these almost invisible spores of the typical adult 

 form and size, these germinal products passing, in their onward growth, through a 

 phase in which a single flagellum, and that the posterior or anchoring one, alone 

 was visible. The illustrations given by Messrs. Dallinger and Drysdale of this 

 interesting genetic reproductive process are reproduced at PL XV. Figs. 22-28. 

 An adult monad, presenting the essential characteristics of the half-developed 

 monoflagellate condition of Heteromita rostrata, recently discovered by the author 

 in salt water, has been previously figured and described under the title of Ancyro- 

 monas marina. 



Heteromita uncinata, S. K. PL. XV. FIGS. 29-41. 



Body smooth, ovate, rounded posteriorly, narrower and slightly curved 

 towards the ventral aspect anteriorly ; anterior vibratile flagellum short, 

 scarcely exceeding one-half of the length of the body, recurved or hooked 

 at its extremity, posterior or trailing flagellum more than twice the length 

 of the body ; contractile vesicle conspicuous, situated near the narrower 

 anterior end ; endoplast at the opposite extremity. Length 1-4000" to 

 1-3000". 



HAB. Fish macerations in an advanced state of putrefaction. 



The foregoing specific name is here proposed for the type figured and described 

 by Messrs. Dallinger and Drysdale * under the title of the " Hooked Monad." Its 

 developmental cycle, as successfully traced by these gentlemen, differs considerably 

 in its details from that of the form last described. Transverse fission, preceded 

 usually by the assumption of a semi-amoeboid condition of the subdividing ani- 

 malcule, constitutes the most simple mode of increase. The more important genetic 

 mode of reproduction was found, however, to consist of the intimate amalgamation 

 not only of two, but often of as many as four or even six individual zooids, the 

 result of such fusion being the production of a larger or smaller spheroidal cyst, from 

 which active monadiform germs of appreciable size, and in many instances already 

 furnished with a single (the posterior) flagellum, were subsequently liberated. This 

 monad is described as progressing rapidly through the water by a series of jerks or 

 springs, which follow each other in constant succession, and are coincident with the 

 movements of the hooked flagellum ; no mention is made of its anchoring itself by 

 the longer and trailing one, though this appendage is doubtless used for such a 

 purpose. The so-called " snapping eyelid " alluded to by Messrs. Dallinger and 

 Drysdale, undoubtedly represents the characteristic contractile vesicle, and in those 

 instances where the anterior flagellum is described as having a knob or knot at its 

 free extremity the animalcule is apparently engaged in withdrawing the organ into 

 the substance of its body previous to the assumption of an amoeboid condition and 

 ultimate encystment. 



The phenomenon of the compound coalescence or genetic union of a plurality 

 of zooids, attested to by the authorities here quoted, in connection with Heteromita 

 vncinata, is of especial interest, on account of the circumstance that a practically 

 identical process of compound coalescence productive of sporular elements or their 

 equivalents on a comparatively colossal scale obtains in the two groups of the 

 Myxomycetes or Mycetozoa and the Spongida. 



In neither of the two species of Heteromita, just described, and for whose discovery 

 and life-history we are indebted to the painstaking researches of Messrs. Dallinger 

 and Drysdale, has any intimation whatever been as yet given respecting their 

 alimentary functions. Had a distinct oral orifice existed, or had the inception 



Monthly Microscopical Journal,' Jan. 1874. 



