GENUS VORTICELLA. 683 



B. — Cuticle distinctly Striate or otherwise ornamented. 



* Bodies conical or elongate. 



Vorticella microstoma, Ehr. 

 Pl. XXXV. Figs. 9-24, and Pl. XLIX. Fig. 27. 



Body somewhat variable in form, usually ovate or subpyriform, about 

 one and a half times as long as broad, but sometimes almost spheroidal ; 

 cuticular surface finely striate transversely ; peristome-border very narrow 

 and constricted, not everted, about one-half of the width of the centre 

 of the body ; pharyngeal cleft greatly prolonged ; pedicle varying from 

 two or three to five or six times the length of the body, usually inserted 

 into a narrower conical posterior prolongation of the body proper. Length 

 1-750" to 1-240". 



Hab. — Stagnant water and infusions ; solitary or in social clusters. 



This species represents one of the most widely distributed members of the genus ; 

 it occurs in ahiiost all water containing decaying vegetable matter, and may be 

 abundantly developed, in company with V. putriniim., from artificial hay-infusions. 

 Under the last-named conditions it usually makes its appearance so early as from 

 a week to ten days after placing the hay to macerate, while the characteristic 

 encystments that give rise to the active animalcules may be detected imbedded in 

 the substance of the hay within a few hours of its first immersion. The species 

 multiplies very rapidly by longitudinal fission, the few first released from the primary 

 cysts soon producing extensive colonies by the constant repetition of this process. 

 Prior to its separation from the parent, a girdle of cilia is produced round the pos- 

 terior extremity of the migrant zooid, which, as it hangs from the parent stalk, 

 presents the aspect of an independent gemmule. It not unfrequently happens 

 that while thus pendent this zooid again subdivides into two of less magnitude, 

 while D'Udekem records and figures one example, see Pl. XXXV. Fig. 19, in 

 Avhich, while yet attached, the migrant animalcule split up into as many as eight 

 minute pyriform zooids, which were presently scattered into the surrounding water. 

 It would seem probable that these rarely produced, more minute zooids represent 

 those whose mission it is to coalesce with the typical sedentary forms, and secure 

 in a sexual generative manner the further multiplication or rejuvenescence of the 

 parent stock, those formed by the simple subequal division of the parent zooid, as 

 a rule, reaffixing themselves, and soon, by the growth of a new pedicle, becoming 

 indistinguishable from the latter. Fuller details of the reproductive phenomena of 

 this species are recorded in the general description of the genus given in a previous 

 page. The striations of the cuticular surface of VoriiccUa microstoma are clearly 

 visible only in association with a careful manipulation of the light, and indeed this 

 surface is represented by many authorities as perfectly smooth and transparent. Both 

 Ehrenberg, and Stein m his earlier writings, figure with this type minute stalked 

 animalcules having a length of less than 1-2000", and which are described as its 

 young. There can be but little doubt, however, that these minute stalked organ- 

 isms are independent flagellate forms, such as Spiimella or Oikomouas, which are 

 abundantly developed in the water that contains this species. On the other hand, 

 the author has never as yet met with examples attaining the largest size given by 

 Ehrenberg, viz. 1-240", the majority of examples observed varying in length from 

 1-750" to 1-600". In infusions containing an abundance of this form the author 

 has frequently met with zooids detached from their pedicles, having no posterior 

 ciliary wreath, but swimming with the aid of their peristomal cilia only, and presenting 

 an inflated subglobose contour, as shown at Pl. XXXV, Fig. 17. These detached 

 zooids were subsequently found to develope into the ovate encystments, with a 



