278 Prof. H. J. Clark on the Cilio- flagellate Infusoria. 



the character of a " nucleolus " or (as is now becoming the be- 

 lief, since the investigations of Balbiani and Claparede) a 

 testicle. 



Reproduction from the egg has not been observed, but trans- 

 verse division occurred in a number of instances. In the latter 

 case it agrees, in the process, with what Allman {loc. cit.) has 

 described, excepting that the resultants (fig. 6, i. ii. ; fig. 7) are 

 quite different in their proportions from the adults (figs. 1, 2, 3). 

 At the moment of separation the young offshoot (fig. 7) is about 

 two-thirds the size of the adult, and is almost as broad as long, 

 and bulges strongly on the ventral side (v), in front of the 

 mouth (m). It has a very flat anterior end, and the pseudo- 

 cuirass [pc) of this part is represented by an inconspicuous 

 unguiform body. The anterior transverse furrow, on account of 

 its narrowness, hardly attracts attention, except along its ventral 

 edge («/), where it is rendered conspicuous by the strong pro- 

 jection of the unguiform cuirass. As in the adult, it is broadest 

 ventrally, but, growing shallower, thins out («/^), going dorsally 

 to almost nothing. The relations and structure of the various 

 organs, cilia, &c., are the same as in the full-grown individuals; 

 but with progressing growth the proportions of the different 

 regions of the body change insensibly, as may be seen by com- 

 paring figures 7, 4, and 1, which are respectively representations 

 of the youngest, middle-aged, and adult individuals. 



EXPLANATION OF PLATE XIL 



[In all the figures the same letters refer to corresponding parts.] 



A. The anterior end of the body. p. The posterior end. 



D. The dorsal side. v. The ventral side. r. The right side. l. The 

 left side. 



af, anterior transverse or annular furrow; af^, dorsal part of af; 

 pf, posterior transverse or annular furrow ; mf, median or longitudinal 

 furrow ; d, depression on the ventral side ; cv, contractile vesicle ; 

 m, mouth, w}, anterior edge of m; ce, oesophagus; dv, digestive vacuoles; 

 fl, pseudo-flagellum, f}, base of ^ ; re, nucleus or generative organ ; ne, en- 

 velope of n (this is the reproductive organ, properly speaking, and n is the 

 contents or reproductive material, the future eggs) ; t, nucleolus or testes ; 

 pc, pseudo-cuirass. 



I., II. The two products of self-division, iii. The annular constriction 

 which finally separates i, and ii. 

 Figs. 1 to 7- Peridinium cypripedium, n. sp. 



Fig. 1. Profile of an adult, seen from the left side ; magn. 500 diams. 

 Fig. 2. View of the ventral side of an adult ; magn. 500 diams. 

 Fig. 3. Posterior view of an adult, the anterior end in the distance ; 



magn. 500 diams. 

 Fig. 4. A young individual; magn. 300 diams. 

 Fig. 5. An adult, gradually dried up ; dorsal view, to show the arrange- 



