PROTOZOA 



31 



possess a girdle of cilia as previously supposed, but that the struc- 

 ture mistaken for cilia is a second flagellum which lies horizontally 

 in the transverse groove. Hence the name Cilioflagellata is super- 

 seded by Dinoflagellata (Gr. dinos, the round area where oxen tread 

 out on a threshing floor). 



19 



FIG. XXII. Dinoflagellata and Rhynchodagellata. X.B. In all these 

 figures the apparent girdle of cilia is, accodring to Klebs and Butschli's 

 recent discovery, to be interpreted as an encircling flagellum lying in the 

 transverse groove. 1. Peridinium uberrimum, Allman ; x 300 (fresh- 



water ponds, Dublin). Probably (according to Butschli) the processes on 

 the surface are not cilia nor flagellum. Both the longitudinal and the 

 transverse groove are well seen. 2. The same species in transverse 



fission. 3. Dinophysis ovata, Cl. and L; x 350 (salt water, Norwegian 



coast). 4. Dinophysis acuminata, Cl. and L. ; X350 (salt water, 



Norwegian coast). 5. Gi/mnodinium, sp. ; x 600. 6. Prorocen- 



trum micans, Ehr.; X300 (salt water). 7. Dorsal aspect of the 



same species. 8, 9. Cysts of Peridinia ; the contents of 8 divided 



into eight minute naked Peridinia; xSOO. 10. Empty cuirass of 



Ceratium divergens. Cl. and L. ; x 500 ; showing the form and disposition 

 of its component plates. 11. The same species with the animal con- 



tracted Into a spherical form. The transverse groove well seen. 12. 



The same species in the normal state. The apparent girdle of cilia is 

 really an undulating flagellum lying in the transverse groove. 13, 14. 



Young stages of Noctiluca miliaris. n, nucleus : s, the so-called spine 

 (superficial ridge of the adult); a, the big flagellum ; the unlettered filament 

 Is a flagellum which becomes the oral flagellum of the adult. 15. Cera- 



tium tnpos, Mull. The transverse groove well seen. The cilia really are 

 a single horizontal flagellmn. 16, 17. Two stages in the transverse 



fission of A octuuca miliaris, Suriray. n, nucleus ; N, food-particles -t the 

 muscular flagellum. 18. Noctiluca miliaris, viewed from the ab'oral 



side (after Allman, Quart. Jour. Mic. Sci., 1872). a, the entrance to the 

 atrium or flagellar fossa (=longitudinal groove of Dinoflagellata) e the 

 superficial ridge; d, the big flagellum (= the flagellum of the transverse 

 groove of Dinoflagellata); h, the nucleus. 19. The animal acted upon 

 by iodine solution, showing the protoplasm like the " primordial utricle" 

 of a vegetable cell shrunk away from the structureless firm shell or 

 cuirass. 20. Lateral view of Noctiluca, showing a, the entrance to the 



groove-like atrium or flagellar fossa in which 6 is placed ; c, the superficial 

 ridge ; d, the big flagellum ; e, the mouth and gullet, in which is seen 

 Krohn a oral flagellum (=the chief flagellum or flagellum of the longitu- 

 dinal groove of Dmo-nagellata) ; /, broad process of protoplasm extending 

 from the superficial ridge c to the central protoplasm ; g, duplicature of 

 the shell in connexion with the superficial ridge ; A, nucleus. 



Butschli further suggests that the Dinoflagellata with their 

 two flagella and their i-shaped combination of longitudinal and 

 transverse grooves may be derived from the Cryptomonadina (see 

 p. 858). In the latter a groove-like recess is present in connexion 

 with the origin of the two flagella. Biitschli thinks the large pro- 

 boscis-like Hagellum of Noctiluca (Rhynehoflagellata) represents 

 the horizontal flagellum of Dinoflagellata, whilst the prominent 

 longitudinal flagellum of the Dinoflagellata is represented in that 

 animal by the small flagellum discovered by Krohn within the 

 gullet (see Fig. XXII. 20, e). The young form of Noetiluca (Fig. 

 XXII. 14) has the longitudinal flagellum still of large size. 



The phosphorescence of many Dinoflagellata is a further point 

 of resemblance between them and Noctiluca. 



Bergh has shown that there is a considerable range of form in 

 various species of Dinoflagellata (Ceratium, &c.), and has also drawn 

 attention to the curious fact that the mode of nutrition (whether 

 holophytic or holozoic) differs in allied species. Possibly it may be 

 found to differ according to the conditions of life in individuals of 

 one and the same species. 



The drawings in Fig. XXII. were engraved before the publication 

 of Butschli's confirmation of Klebs's discovery as to the non-existence 

 of cilia in the transverse groove. The hair-like processes figured 

 by Allman (91) external to the transverse groove in his Peridinium 

 uberrimum (Fig. XXII. 1, 2) cannot, however, be explained as a 

 flagellum. Biitschli inclines to the opinion that their nature was 

 misinterpreted by Allman, although the latter especially calls 

 attention to them as cilia, and as rendering his P. uberrimum 

 unlike the Peridinium of Ehrenberg, in which the cilia (horizontal 

 flagellum) are confined to the transverse groove. 



y.B. See Fig. XXVII., and esplanation, p. 37. 



CLASS IV. BHYNCHOFLAGELLATA, Lankester. 



Characters. Corticate Protozoa of large size (^V tn inch) and 

 globular or lenticular form, with a firm cuticular membrane and 

 highly vacuolated (reticular) protoplasm. In Noctiluca a deep 

 groove is formed on one side of the spherical body, from the bottom 

 of which springs the thick transversely striated proboscis or 

 "big flagellum." Near this is the oral aperture and a cylin- 

 drical pharynx in which is placed the second or smaller flagellum 

 (corresponding to the longitudinal flagellum of Dinoflagellata). 



Nutrition is holozoic. No contractile vacuole is present ; granule- 

 streaming is observed in the protoplasm. An alimentary tract and 

 anus have been erroneously described. The nucleus is spherical 

 and not proportionately large (see for details Fig. XXII. 18 to 20). 



Reproduction by transverse fission occurs, also conjugation and, 

 either subsequently to that process or independently of it, a forma- 

 tion of spores (Cienkowski, 87), the protoplasm gathering itself, 

 within the shell-like cuticular membrane, into a cake which divides 

 rapidly into numerous flagellated spores (flagellulse). These escape 

 and gradually develop into the adult form (Fig. XXII. 13, 14). 



The proboscis-like large flagellum is transversely striated, and 

 exhibits energetic but not very rapid lashing movements. 



Noctiluea is phosphorescent, the seat of phosphorescence being, 

 as determined by Allman (86), the cortical layer of protoplasm 

 underlying the cuticular shell or cell-wall as the primordial cuticle 

 of a vacuolated vegetable cell underlies the vegetable cell-wall. 



Genera. Only two genera (both marine) are known : Noctiluca, 

 Suriray (90) (Fig. XXII. 17-20) ; Leptodiscus, Hertwig (88). 



Further Remarks on the Khynchoflagellata. The peculiar and 

 characteristic feature of Noctiluca appears to be found in its large 

 transversely-striated flagellum, which, according to Butschli, is not 

 the same as the longitudinal flagellum of the Dinoflagellata, but 

 probably represents the horizontal flagellum of those organisms in 

 a modified condition ; hence the name here proposed Rhyncho- 

 flagellata. 



Noctiluca is further remarkable for its large size and cyst-like 

 form, and the reticular arrangement of its protoplasm, like that of 

 a vegetable cell. This is paralleled in TracheJius ovum among the 

 Ciliata (Fig. XXIV. 14), where the same stiffening of the cuticle 

 allows the vacuolation of the subjacent protoplasm to take place. 

 The remarkable Leptodiscus medusoides of R. Hertwig (88) appears 

 to be closely related to Noctiluca. 



It would no doubt be not unreasonable to associate the Dino- 



