GENUS GLAUCOMA. 795 



fications into an Aspidisca, undistinguishable from the adult forms abundantly 

 present with it in the surrounding water. Simultaneously with the growth of the 

 ventral and anal styles, the fine vibratile ventral cilia and terminal hair-like setae 

 were gradually absorbed and obliterated, the vibrating oral membrane unrolled and 

 extended itself, became transversely stnate at regular intervals, and eventually split 

 up to form the characteristic adoral fringe of cilia. The whole of these metamorphoses 

 occupied a space of less than an hour, the animalcule at this early stage of its 

 adolescent career being, however, decidedly weak on its " legs," as its locomotive 

 styles may be appropriately designated, and staggering about after the manner 

 of a newly-born calf or colt. Both in its adult -and larval or Glaucoma stage 

 Aspidisca costata exhibits an eccentricity of gait, which may be cited as correlative 

 evidence in demonstration of their identity. This peculiarity alluded to is manifested 

 by the tendency of the animalcule in either case to rotate upon a fixed point as 

 though upon a pivot, or to persevere in the maintenance of a restricted circuitous 

 course within the area of the microscopic field ; the action in this latter instance 

 is highly suggestive of the gait exhibited by a playful child as it pushes itself 

 round and round in a circle, one leg only being permitted to exert a locomotive 

 function. 



With reference to the foregoing observation, the author, in place of conceding 

 to the genus Glaucoma the rank of an independent generic type, is inclined to regard 

 its members as mere larval conditions of Aspidisca and other allied Hypotricha. 

 To which species the Glaucoma scintillans of Ehrenberg ultimately develops has yet 

 to be determined. In accordance, nevertheless, with Stein's more recent drawings 

 and description of this type, the oral aperture is situated near the anterior extremity, 

 and the contractile vesicle at the opposite end, and from these circumstances it may 

 be predicted as more likely representing the earlier stage of a Euplotes or 

 Uronychia, in both of which the oral orifice is more anteriorly located than in 

 Aspidisca. The bi-labiate structure of the oral membrane of Glaucoma, as described 

 by Stein and Claparede and Lachmann, is evidently a misinterpretation of the optical 

 aspect of a revolute single lamina. No trace of an endoplast could be detected by 

 the author in the Glaucoma condition of this species, and only in the older 

 examples of the adult Aspidisca. Increase by transverse fission was frequently 

 observed during this embryonic phase, such circumstance demonstrating that this 

 reproductive process is not confined to the adult stage, and is therefore not 

 diagnostic of it even among the higher Ciliata. The diagnosis of the genus 

 Glaucoma, with its two species herewith subjoined, as also that of the genus Micro- 

 thorax of Engelmann, are allotted, in this treatise, a provisional status only, being 

 regarded by the author as representing, in all probability, mere transitional or 

 embryonic phases of higher Hypotrichous forms. 



GENUS II. GLAUCOMA, Ehrenberg. 



Animalcules free-swimming, persistent in shape, more or less ovate, with 

 a convex and frequently grooved dorsal and a plane or flattened ventral 

 surface ; oral aperture ventral, associated with a minute, vibrating, flap-like 

 membrane ; fine vibratile cilia more or less completely clothing the ventral 

 surface, these occasionally supplemented by one or more hair-like caudal 

 setae. 



Glaucoma scintillans, Ehr. PL. XLV. FIGS. 39 AND 40. 



Body ovate, depressed, the margin entire and equally rounded at the 

 two extremities ; the oral aperture with its projecting vibratile membrane 

 developed towards the anterior extremity ; the contractile vesicle posteriorly 

 located ; cilia projecting all round the periphery as a marginal fringe, and 



