404 ORDER FLA GELLA TA-EUSTOMA TA. 



GENUS IV. CRYPTOMONAS, Ehrenberg. 



Animalcules free-swimming, illoricate, persistent in form, more or less 

 ovate or elongate ; flagella two in number, subequal, issuing from beneath 

 a prominent, anterior, lip-like process ; oral aperture conspicuous, opening 

 close to the base of the flagella, continued backwards as a distinct tubular 

 pharynx; endoplasm enclosing two lateral, longitudinally placed colour- 

 bands ; contractile vesicle and endoplast conspicuous. Inhabiting fresh 

 water. 



The animalcules of this genus, excepting for the presence of the endoplasmic 

 colour-bands, correspond in form and structure with those of Chilomonas. 



Cryptomonas ovata, Ehr. PL. XXII. FIGS. 16-18. 



Body elongate-ovate, compressed, usually narrowest and sometimes 

 recurved towards the dorsal aspect posteriorly, about three times as long as 

 broad ; oral aperture large ; pharyngeal passage conspicuous, tubular, con- 

 tinued backwards beyond the centre of the body ; colour-bands bright green, 

 mostly developed on the dorsal and ventral aspects throughout the entire 

 length of the body ; contractile vesicle situated immediately above the 

 commencement of the pharynx; endoplast posteriorly located. Length 

 1-600" to 1-400". HAB. Fresh water, amongst Conferva. 



As shown by Stein's figures,* here reproduced, PI. XXII. Fig. 18, the young of 

 this species differ from the adults in possessing a flexible body and an acuminately 

 pointed, recurved posterior extremity ; the characteristic colour-bands are also limited 

 during the earlier stages of growth to two green, subcentral, ovate corpuscles, which 

 gradually assume a band-like outline as growth progresses, and finally extend through- 

 out the length of the body. In those adult individuals which possess a recurved 

 posterior region, it is explained by Stein that the cuticular surface has become 

 indurated while retaining more nearly the external contour of the embryonic stage ; 

 these more exceptional examples which present a somewhat sigmoid flexure, have 

 been described by Ehrenberg as a distinct species under the title of Cryptomonas 

 curvata. 



Cryptomonas erosa, Ehr. PL. XXII. FIGS. 19-21. 



Body elongate-ovate, compressed, about twice as long as broad, the 

 posterior extremity bluntly rounded, recurved slightly towards the ventral 

 aspect ; pharyngeal tube scarcely produced to the centre of the body ; 

 colour-bands light green ; contractile vesicle and endoplast as in C. ovata. 

 Length 1-960". HAB. Fresh water, among Conferva. 



This species may be distinguished from C. ovata by its shorter proportional 

 length, smaller size, and ventral curvature of the posterior extremity. By Stein's 

 figures it is shown to divide by longitudinal fission after the manner of Chilomonas. 

 The nucleus or endoplast in both this and the preceding type exhibits reproductive 

 phenomena corresponding with those presented by Euglena and Phacus. By con- 

 centration, around this structure, of the substance of the endoplasm, or through 



1 Infusionsthiere,' Abth. iii., 1878. 



