250 Prof. H. James-Clark on the Spongise ciliatse 



in tlie Exe and in the canal near Exeter, throughout the summer 

 months ; but, by attaching itself to plants which die down in 

 the autumn, the specimens are all swept away by the winter 

 floods. 



XXXIII. — On the Spongiae ciliataB as Infusoria flagellata; or 

 Observations on the Structure, Animality, and Relationship 

 of Leucosolenia botryoides, Bowerhanh. By H. James- 

 Claek, A.B., B.S., Professor of Natural History in the 

 Agricultural College of Pennsylvania. 



[Continued from p. 216.] 

 § 12. Astasia trichophora. Clap. PI. VI. figs. 45, 46. 

 The transition from the mononematous Monas, Godosiga^ 

 Leucosolenia, &c. to those heteronematous Flagellata which 

 possess at the same time a proboscidiform and a gubernacli- 

 form flagellum is most aptly exemplified by that curious mi- 

 metic combination of Amoeba and Anisonema known as As- 

 tasia trichophora, Clap. [TracheUus trichophorus , Ehr.). At 

 first sight it appears to be capable of all the abrupt retrogres- 

 sive motions and short turnings of sa\ Anisonema (figs. 65-69), 

 without being endowed with a similar means of locomotion. 

 One is not long, however, in discovering the homologue of the 

 t7'ail {fl.^) or rudder [guhernaclum) of the latter in the posterior 

 abdominal, triangular prolongation (fig. 45, fl"^) of the body of 

 the former. That this is the true interpretation of the pro- 

 longation is warranted not only by the use to which it is put, 

 as a sort oi point d^ippui during the amoeboid retroversions of 

 the body, but also by its persistent form whilst the animal is 

 contorted into a shapeless writhing mass. In the midst of the 

 paucity of distinctive topography, we are also furnished by 

 this organ, if I may so call it, with a basis of ready discrimi- 

 nation between the practically ventral and dorsal sides of the 

 body ; for, although it may not lie strictly in the central line 

 of progress during reptation (nor could we expect to find it 

 there upon being referred to its homological relation to the 

 asymmetrically attached guhernaclum oi Anisonema) , it none 

 the less belongs to the reptant side of the animal, and, as it 

 were, controls its motions and acts as a keel, upon which the 

 posterior end of the body vibrates and reels from side to side. 

 Finally, in reference to this point, it may be added that this 

 species does not swim, properly speaking, nor has it the cha- 

 racter of the revolving natant forms, such as Dujardin sepa- 

 rated from the Astasia of Ehrenberg and described under the 

 name of Peranema. 



