THE INFUSORIA 



421 



a new stalk and return to the Podophrya condition. If other species 

 have a similar life -history, as is very probable, our classification 

 must be regarded as quite provisional. 



The Acinetaria contain the following families according to the 

 classification of Sand : 



Family DENDROCOMETINA, Stein. Epizoic Acinetaria of medium 

 size without a peduncle. Hemispherical or lenticular in shape. Numerous 

 tentacles arranged in several bundles, the individual tentacles being fused 

 together for the greater part of their course to form the "arms," but 

 independent at their free extremities. Each contains a single contractile 

 vacuole. Reproduction by the formation of a single endogenous gemmula. 

 Dendrocometes, Stein, is found on the 

 gills of Gammarus pulex. In Europe /^ 



the gills of this species appear to be 

 very rarely free from this epizoon, and 

 sometimes bear them in great numbers "Cb~^ "J^ A 



B 



Free-swimming gemmulae of Den- 

 drocometes paradoxus, Stein, as seen, 

 A, from the side, B, from below. M, 

 meganucleus; in, micronuclei ; c.v, 

 contractile vacuole. (After Butschli. 

 The micronuclei have been added by 

 the author from original prepara- 

 tions.) x ca. 300. 



Fio. 85. 



Dendrocometes ^aradoxus, Stein. 

 Epizoic on the gill -jf Gammarus. , 

 meganucleus ; b, contractile vacuole; 

 c, a small organism paralysed and 

 held fast by one of the arms, x 350. 



(Fig. 85). Stylocometes, Stein, is found on the gills of Asellus aquaticus 

 and, rarely, on the gills of Gammarus and on colonies of Ophrydium. It 

 differs from Dendrocometes in having more numerous arms (10-12). 



Family DENDROSOMINA, Butschli. Characterised by the lobed or rami- 

 fied form of the body, each lobe or branch bearing a number of suckers. 

 There is no peduncle. Trichophrya, Clap, and L. The body is lobed, ovoid, 

 or hemispherical in shape. It is sometimes attached at one point or disc, 

 but sometimes free and amoeboid. When the body is distinctly lobed 

 the suckers are confined to the free ends of the lobes ; in other forms the 

 tentacles are more irregularly scattered. There are nine species, and they 

 are found on the gills oi fish (perch and pike), on the abdominal segments 

 of Cyclops, on Epistylis, Conferva, Anacharis, on Salpa, on Algae, Hydroids, 

 etc. Dendrosoma, Butschli. This form (Figs. 32 and 87) reaches to a 

 considerable size, 2 -4. In its fully developed condition it consists of a 

 number of long lobes of branches rising from a creeping stolon. There is 

 a continuous axial meganucleus extending throughout the branches of the 

 stolon and the upright lobes. At the extremity of each lobe there is a 



