4:0 THE MICROSCOPE AND ITS REVELATIONS. 



naked. In one curious form, the Ophiodendron, the suckers are borne 

 in a brush-like expansion on a long retractile proboscis-like organ. ,And 

 the rare Dendrosoma, whose size is comparatively gigantic, forms by con- 

 tinuous gemmation an arborescent 'colony,' of which the individual 

 members remain in intimate connection with one another. 



434. Multiplication in this group seems occasionally to take place by 

 longitudinal fission; but this is rare in the adult state. Sometimes exter- 

 nal gemmce are developed by a sort of pinching-off of a part of the free 

 end of the body, which includes a portion of the nucleus; the tentacula 

 of this bud disappear, but its surface becomes clothed with cilia; and, 

 after a short time, it detaches itself and swims away comporting itself 

 subsequently like the internal embryos, whose production seems the more 

 ordinary method of propagation in this type. These originate in the 

 breaking-up of the nucleus into several segments, each of which incloses 

 itself in a protoplasmic envelope; and this becomes clothed with cilia, by 



FIG. 302. 



Suctorial Infusoria: l,Conjugation of Podophrya quadripartita; 2, Formation of embryos 

 by enlargement and subdivision of the nucleus; 3, Ordinary form of the same; 4, Podophrya 

 elongata. 



the vibrations of which the embryos are put in motion within the body 

 of the parent (Fig. 302, 2), from which they afterwards escape by its 

 rupture. In this condition (a) they swim about freely, and seem identical 

 with what has been described by Ehrenberg as a distinct generic form, 

 Megatriclia. And according to the recent observations of Mr. Badcock, 1 

 these Megatricha-foYms multiply freely by self-division. After a short 

 time, however, they settle down upon filamentous Algae or other supports, 

 lose their cilia, put forth suctorial tentacles (which seem to shoot out 

 suddenly in the first instance, but are afterwards slowly retracted and 

 protruded with a kind of spiral movement), and assume a variety of 

 amoabiform shapes (Fig. 303, 1, 2, 3), some of them corresponding to 

 that of the genus Triclwphrya. In this stage they become quiescent at 



1 " Journ. of Roy. Microsc. Soc.," Vol. iii. (1880), p. 563. 



