of the alio -flagellate Infusoria. 277 



genuine cuirass. Where vibratile cilia are present, no such 

 covering can be said to exist ; and as the broad anterior end (a) 

 of the body is devoid of them, its skull-cap covering is the only 

 portion of the derm where one could expect to find a cuirass. 

 But this it is only in form, since it participates with the rest of 

 the body in the general expansion when an individual is dying. 

 It has, without doubt, a different character from the rest of the 

 skin ; for the style of ornamentation is not of the same kind, 

 and, curiously enough, too, it is less truly ornamented than 

 the other regions of the body, amounting to a mere scattered 

 punctuation ; whereas over the field whei-e the cilia prevail these 

 punctuations, which are in reality minute, cylindrical, strongly 

 refracting bodies standing perpendicularly to the surface of the 

 derm, are arranged in perfectly regular rows, which have a dif- 

 ferent character in the three regions posterior to the pseudo- 

 cuirass. In the space (fig. 5 d) between the anterior [af) and 

 posterior {pf) transverse furrows, the rows trend longitudinally 

 and transversely; in the posterior transverse furrow [pf) they 

 have the same arrangement as the last, but they are more closely 

 set together; and in the region behind the latter furrow they 

 trend in decussating lines (p), like those in the carapace of 

 Arcella vulgaris. 



This region is also characterized by being divided longitudi- 

 nally, on the ventral side, by a furrow (fig. 1, 2, 6 mf) which 

 trends in a direct line from the end of the body to the mouth, 

 and gradually widens anteriorly, where it joins the annular 

 transverse furrow {pf). At this point of juncture the flagellar 

 appendage arises, and opposite to it the anterior edge of the 

 transverse furrow just mentioned forms an inequilateral angle at 

 the broader margin {m}) of the mouth, so that the right and left 

 halves of this furrow are rendered asymmetrical — a character in 

 perfect accordance with that of many, if not of all, the Peridinia. 



The Nucleus {?i) . — At the period when these observations were 

 made, viz. early last December, the genital organ invariably lay 

 transverse to the longitudinal axis, and occupied a very large 

 portion of the bulk of the posterior end of the body. Most 

 frequently it had a U-shaped form (fig. 3 w), and embraced the 

 contractile vesicle with its two limbs. It was then of a yellowish- 

 brown colour, and perfectly homogeneous. Occasionally it was 

 observed to be divided into three or four masses, which extended 

 toward the region encompassed by the posterior annular furrow. 

 While in the U-shaped form, the whole semiopaque mass was 

 enclosed in a transparent envelope (ne). Oftentimes there was 

 to be seen immediately over and close to the dorsal region of the 

 nucleus, and directly in the plane of the axis of the body, a mi- 

 nute, clear, vesicular corpuscle (fig. 3 i), which seemed to have 



