. The Cambridge natural history. Zoology. FLAGELLATA 133 eiices, of which one, a little firmer than the other, and trans- versely ridged, is called the tooth; at the junction of the two is a second, minute, flagellum, usually called the cilium. Behind these the oral groove has an oval space, the proper mouth; behind this, again, the oral groove is continued for some way, with a distinct rod-like ridge in its furrow. The whole body, including the big flagellum, is coated by a strong cuticular pellicle, except at the oblong mouth, and the lips and rod are mere thickenings of this. The cytoplasm
. The Cambridge natural history. Zoology. FLAGELLATA 133 eiices, of which one, a little firmer than the other, and trans- versely ridged, is called the tooth; at the junction of the two is a second, minute, flagellum, usually called the cilium. Behind these the oral groove has an oval space, the proper mouth; behind this, again, the oral groove is continued for some way, with a distinct rod-like ridge in its furrow. The whole body, including the big flagellum, is coated by a strong cuticular pellicle, except at the oblong mouth, and the lips and rod are mere thickenings of this. The cytoplasm has a reticulate arrangement: the mouth opens into a central aggregate, from which strands diverge branching as they recede to the periphery, where they pass into a continuous lining for the cuticular wall, liquid filling the interspaces. The whole arrangement is not unlike that found in many plant- cells, but the only other Protists in which it occurs are the Ciliata Trachelius (Fig. 56, p. 153) and Loxodes. The central mass contains the large nucleus. Noctiluca is an animal feeder, and expels its excreta through the mouth. The large flagellum is remarkable for the transverse striation of its plasma, especially on the ventral side. The cuticle may be moulted as in the Dinoflagellates. As a prelude to fission the external differentiations disappear, the nucleus divides in the plane of the oral groove, and a meridional constriction parts the two halves, the new external organs being regenerated. Conjugation occurs also, the two organisms fusing by their oral region; the loco- motive organs and pharynx disappear; the conjoined cytoplasms unite to form a sphere, and the nuclei fuse to form a zygote or fertilisation nucleus. This conjugation is followed by sporu- Jation or brood-formation.^ ' This process has the character of telolecithal segmentation in a Metazoan Fig. 48.—JVoctSuca miliaris, a marine Cysto- flagellate. (Prom Verivorn.). Please note that these images are e
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
