784 MICROSCOPIC FORMS OF ANIMAL LIFE 



of the latter is naked. In one curious form, the Opfoybdehdron, the 

 suckers are borne in a brush-like expansion on a long retractile 

 proboscis- like organ; and the rare Dendrosoma, whose size is com- 

 paratively gigantic, forms by continuous gemmation an arborescent 

 * colony,' of which the individual members remain in intimate 

 connection with one another. 



Multiplication in this group seems occasionally to take place by 

 transverse fission, but this is rare in the adult state. Some- 

 times external 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 be- 



FIG. 598. Suctorial Infusoria: 1, Conjugation of 



quadripartita ; 2, formation of embryos by enlargement and sub- 

 division of the nucleus ; 3, ordinary form of the same ; 4, Podo- 

 pliryci elongdta. 



comes 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 

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

 body of the parent (fig. 598, 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 



1 Now called, after Biitschli, Tokophrya,on account of its mode of reproduction ; 

 see his Protozoa, p. 1928. 



