GENUS MALLOMONAS. 465 



ornamented or shagreened with closely approximated hemispherical elevations, each 

 of which forms a basis of support to the overlying seta. In this respect the cuticular 

 investment of Mallomonas exhibits a structure corresponding closely with that 

 of many Holotrichous Ciliata, in which the cilia or setae spring from similar 

 hemispherical cuticular elevations, the cuticle however, in most instances, remaining 

 soft and plastic. Examined in the living state the animalcules were found to exhibit 

 diverse phases of comportment. Sometimes they remained quiescent, with the flagel- 

 lum entirely retracted within the perforation or oral cleft at the anterior extremity 

 of the hardened cuticle, while at other times this organ was extended and rapidly 

 undulated or vibrated. In the former of these instances the quiescent animalcule 

 with its extended setae and retracted flagellum, except for its colour, presents an 

 aspect closely similar to that of the Holotrichous Cychdium glaucoma. On abandoning 

 this quiescent for a motile state, the hitherto erectly extended setae are, as the 

 animalcule progresses in an even, straightforward course through the water, reflected 

 backwards, as shown at PI. XXIV. Fig. 73. At first it seemed as though the little 

 creature possessed an active control over these appendages, and could erect or 

 depress them at will. The subsequent determination, however, of the relationship 

 subsisting between the setae and the indurated cuticle, as already described, 

 precludes such an interpretation, and it is evident that this reflection of the 

 setae must be accounted for simply by their yielding before the pressure of the 

 water during locomotion. 



The interior parenchyma or endoplasm of the specimens examined was found to 

 consist of an apparently homogeneous, clear, greenish-yellow plasma, one or two 

 slowly contracting vacuoles within the same being detected towards the posterior 

 extremity of the body. Other vacuolar spaces, of a non-contractile order, were 

 scattered irregularly throughout its substance. By Perty the animal or vegetable 

 nature of Mallomonas was left undecided. Although the inception of food-particles 

 was not witnessed, the evident control exerted by this organism in its movements 

 leaves no doubt as to its true animal nature. 



Stein * has attempted to identify Mallomonas Plosslii with the disintegrated and 

 metamorphosed zooids of Synura uvella. Such an identification, however, in face 

 of the evidence here brought forward," cannot be maintained. Mallomonas 

 proper never possesses but a single flagellum, while the characteristic setae exhibit 

 a uniform size and symmetrical plan of disposition altogether distinct from that 

 pertaining to the metamorphosed zooids of Uvella, as figured by this authority. 



Supplementary Species. 



Fresenius f has figured and described an animalcule which he refers to this form, 

 which on further investigation will probably prove to be a second species. The 

 hair-like setae in this type are represented as fully equal in length to or longer than 

 the body, and comparatively few, thirty being the greatest number counted by him, 

 while considerably less are given in his figures ; the two anterior of these are, 

 however, described as being usually directed forwards, like antennae, on each side 

 of the flagellum. It is proposed to provisionally distinguish this animalcule by the 

 title of Mallomonas Fresenii. A delineation of this species or variety, reproduced 

 from the figures of Fresenius, is given at PI. XXIV. Fig. 74. 



Fam. IV. STEPHANOMONADID-ffi, S. K. 



Animalcules free-swimming, bearing a single terminal flagellum, the 

 base of which is embraced by a brush-like fascicle or uninterrupted circular 

 wreath of cilia. 



* ' Infusionsthiere,' Abth. iii., 1878. 



t ' Beitrage zur Kenntniss mikroskopischer Organismen,' Frankfort, 1858. 



2 H 



