278 Prof. II. J. Clark on the Cilio-jlagellate 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. n. ; 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 {(if), 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 (of 1 ), 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 XII. 



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



A. The anterior end of the hody. v. The posterior end. 



r>. The dorsal side. v. The ventral side. r. The right side. L. The 

 left side. 



of, anterior transverse or annular furrow ; of 1 , 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, to 1 , anterior edge of to ; ae, oesophagus; dv, digestive vacuoles; 

 ji, pseudo-fiagellum,^ 1 , base of^; n, nucleus or generative organ ; we, 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, in. 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. 

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



