GREOARINiE, INFUSORIA. 
485 
3. Lankestbb, E. Ray. Remarks on the structure of the 
GregaritKB and on the development of G. (Monocystis) 
sipunculiy Kdll. Q. J. Micr. Sc. xii. pp. 342-351, pi. 20. 
Ill the adult G. gigantea, Van Bbneden (1, 2) distinguishes the following 
layers : — (1) A central medullary parenchyma, appearing as a dark band occu- , 
pying the axis of the body, and composed of a granular substance, much more 
fluid than (2) the cortical parenchyma, a slimy protoplasmic matter, less gra- 
nular and clearer. The longitudinal striation often observed is due to ridges 
and channels of the inner layer j but they will appear and disappear, and are 
only to be regarded as momentary foldings, not as being of a muscular nature. 
(3) A thin layer, containing numerous regular transverse fibrils or rings, to 
which the author ascribes the character of true muscular fibres. This layer 
forms also the partition against the anterior chamber, but only invests its 
basal portion. (4) The cuticular layer. Having demonstrated this high degree 
of diflerentiation in a monocellular organism, the author asks whether the 
Infusoria might not also be monocellular animals, as was once believed. 
Lankesteb (3) criticizes Van Beneden’s conclusions regarding the mus- 
cular layer. It is absent in many GregarincCy and when present affords no 
evidence of contractility : it is, according to Lankester, only internal thicken- 
ings of the cuticular layer. The seat of contractility is in the cortical layer, 
as demonstrated in Monocystis ascidice and nereidis (pi. 20. figs, 1 & 2), where 
the cortical layer in the anterior portion of the body is fibrous and eminently 
mobile. Lankester has further examined M, sipunculiy found free, floating, 
or encysted in the visceral cavity of Sipunctdus nudus, and figures various 
stages in its development, answering perfectly to those observed by Von 
Beneden in the gregarine of the lobster ,* the amoeboid stage, however, wos 
not observed ; but (1) pseudonaviculm with a single immobile filament, 
(2) monerinn paoudofilarian forms, (3) psoudoccrcarioo, with a motionless 
nucleated head and a vibratile structureless tail, (4) monocystic gregarincs 
multiplying by longitudinal fission, (6) monocystic bean-shaped gregarines 
of of an inch in length, (Q) free and encysted monocystic gregarines, 
attaining a diameter of | of an inch (1. c. pi. 20. figs. 3-18), were observed.^ 
The pseudonaviculae ” of M. seenuridis are also described and figured 
(fig. 19). 
Van Beneden’s previous researches on the evolution of Gregarines are 
reprinted in J. Zool. i. pp. 134-106, and an abstract given in Arch, Sci. Ifat. 
1872, pp. 256-260, translated in Ann. N. II. (4) x. pp. 309-312. 
INFUSORIA. 
1. Bastian, H. C. On some heterogenetic modes of origin of 
flagellated Monads, Fungtls-gerras, and Ciliated Infusoria. 
P. R. Soc. XX. pp. 239-264. 
Among the author’s observations on the development of small organisms 
in the ** proligerous pellicle ” forming on the surface of an infusion of hay ex- 
posed to the air, two may be especially noticed, viz.; — the development of , 
1872. [voi. IX.] 2 k 
