632 ORDER PERITRICHA. 



Halteria grandinella, Miill. sp. PL. XXXII. FIGS. 35-38. 



Body subglobose, transparent, .usually terminating posteriorly in a 

 somewhat narrower obtusely rounded point ; springing-setae very long and 

 fine, forming a central girdle, but not situated in an equatorial groove or 

 furrow, the circle of adoral cilia exhibiting at one point a short interruption 

 or spiral involution ; contractile vesicle and endoplast spherical, located 

 close to each other near the centre of the body. Length 1-1500" to 1-860". 



HAB. Pond water. 



This species, while receiving its characteristic generic title from Dujardin, is 

 identical with the Trichoda and Trichodina grandinella of O. F. Miiller and Ehren- 

 berg. It is of common occurrence in pond water, and has been described and por- 

 trayed by almost all the earlier writers. With the exception, however, of those by 

 Claparede and Lachmann, none of these figures or descriptions given are to be 

 relied upon, all having misinterpreted the true form and structure of both the oral 

 ciliary wreath and that central girdle of setse by which the animalcule accomplishes 

 its leaping movements. As first shown^by Miiller, Halteria grandinella increases by 

 transverse fission, the process of separation into two of a single individual being 

 extremely rapid. When examining examples of this or< other species of the genus, 

 Claparede and Lachmann recommend the introduction upon the same slide of a few 

 suctorial Acinetae. Against these the Halterias are sure to strike while making 

 their characteristic bounds, and being immediately seized and held immovably, an 

 unprecedented opportunity is afforded for studying their structural characters. In 

 a gathering containing a large number of these animalcules recently collected in the 

 neighbourhood of St. Heliers, Jersey, the author found associated with them nume- 

 rous examples of a species of Urotricha closely allied to, if not identical with, 

 U. farcta. Their dimensions equalled about one-half that of the Halterias, while 

 their rolling and springing movements corresponded so closely with those of their 

 larger comrades, that it is considered highly probable by the author that Urotrich a 

 may eventually prove to be an immature or larval condition only of Halteria. 



Halteria volvox, Eichwald sp. PL. XXXII. FIG. 39. 



Contour of body as in H. grandinella, but rather larger ; leaping-hairs 

 taking the same form and position, but supplemented by an equatorial 

 zone of long, recurved, filamentous cilia. HAB. Fresh water. 



Claparede and Lachmann observed this species as here figured on one occasion 

 only, and refer it with some doubt to the Trichodina volvox described in Eichwald's 

 ' Infusorienkunde Russland,' 1852. 



Halteria viridis, From. 



Body globose, anteriorly truncate, surface smooth, colour green ; 

 median circlet of setae very stout and conspicuous ; motion rotatory and 

 leaping. Length 1-1600". HAB. Fresh water. 



Halteria verrucosa, From. 



Body subspherical, truncate anteriorly, acuminately pointed posteriorly, 

 having a central depression on one side which imparts to it a gibbous 

 contour ; colour green. Length 1-600". HAB. Fresh water. 



