GENUS STROMBIDIUM. 



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Halteria lobata, From. 



Body globose, the frontal margin projecting in the form of three raised 

 papillse ; colour green ; movements very swift. Length 1-800". 

 Hab. — Fresh water. 



Supplementary Species. 



As many as five additional species are added to the genus Halteria by De 

 Fromentel,* in none of which, however, with one exception, are the characters given 

 sufiiciently distinct for separate specific recognition. This exceptional form, his 

 H. bipartita, is, however, not a Halteria, but apparently belongs to the genus Arach- 

 nidiiim. The Halteria pulex of Claparede and Lachmann is evidently referable to 

 Stein's genus Mesodinium. 



Genus II. STROMBIDIUM, C. & L. 



Animalcules free-swimming, globose, or turbinate ; oral aperture termi- 

 nal, eccentric, associated with a spiral wreath of powerful, erect, cirrose 

 cilia ; no accessory springing-hairs ; endoplast and contractile vesicle 

 conspicuous. Inhabiting salt and fresh water. 



The animalcules of Strombidiiim surpass those of Halteria in the restlessness 

 and rapidity of their movements, much difficulty consequently attending the inter- 

 pretation of the true nature of their oral system. Claparede and Lachmann have, 

 however, decided that the peristomal cirri in Strombidiiim turbo describe an incom- 

 plete spiral course, while Stein expresses a similar opinion with reference to the 

 several types that have fallen under his observation. The investigations of the 

 present author have elicited that a like disposition of the adoral cirri obtains in 

 various other species, which may therefore now be accepted as diagnostic of the 

 genus. This spire, furthermore, coincides with that of Halteria, it being its right 

 limb that is involute and descends into the oral fossa. Excepting for the absence of 

 the equatorial springing-setse, this genus might be compared with the one last named, 

 but in the length and shuttlecock-like disposition of the adoral cirri its members 

 still more nearly resemble those of Tintinniis, and with which they are more imme- 

 diately united through Strombidinopsis. The movements of the animalcules of the 

 genus Strombidiiim consist of a vigorous oscillating or rolling motion to and fro, as 

 though on a pendulum, interrupted, mostly when disturbed, by locomotion in a straight 

 line, combined with rapid rotation on their longitudinal axis. A similar oscillating 

 comportment has been already reported of Strombidinopsis and Calceolus, and recurs 

 again in Urocentrum and Gyrocoris. When exchanging their oscillatory or rotatory 

 motion for a rectilinear course, the likeness of these animalcules to detached roving 

 Vorticellcs is very noteworthy ; the earlier phases of Vorticella nebiilifera, as elicited 

 by the recent investigations of Everts, as delineated at PI. XXXV. Fig. 39, are 

 furthermore scarcely distinguishable from the matured zooids of Strombidiiim turbo 

 or S. Claparedi. 



Strombidium sulcatum, C. & L. Pl. XXXII. Fig. 47. 



Body subglobose, truncate, and longitudinally furrowed posteriorly ; 

 adoral cilia stout, equalling; half the body in length ; contractile vesicle 

 spherical, subcentral ; colour brownish yellow. Length 1-400". 



Hab. — Salt water : Bergen (C. & L.). 



* ' Etudes sur les Microzoaires,' Paris, 1876. 



