34 Prot. 
XVIII. PROTOZOA. 
Morphology of the Coccolithoplioridse. The body is enclosed in three 
envelopes, most internally a delicate membrane, then a transparent 
gelatinous envelope, and externally the shell, composed of peculiar and 
varied calcareous plates, the Coccoliths. The cell-body possesses a nucleus, 
one or two flagella, and two yellowish chromatophores, each of which is 
accompanied by a strongly-refractile body, Lohmann (231). 
Infusoria:—Description of a new Infusorian, Monomastix ciliatiis, 
with vibratile cilia and a whip-like flagellum, Roux (321 & 322). 
General account of :—Anoplophrya circulans , and Hoplitophrya lumbrici , 
from Lumbricus , Bertolotti (30); Herpetophrya astoraa , n. g., n. sp., a 
Holotrichous Ciliate lacking mouth and contractile vacuole, Siedlecki 
( 359); the family Halterina Clap. & Lachm., Averintzev (12); Stylonichia 
pustulata , (encystment), and also of Oxytricha pellionella, Prowazek (300). 
Notes on Phacodinium muscorum, a new Hypotrichous Ciliate, Prowazek 
(301). 
2. Minute structure of cell-organs. 
(a) Membrane, test, shell :—Penard (286) does not agree with 
Rhumbler in supposing that growth of the shell takes place in various 
Thecamoebidce ( Testacea), at any rate to any appreciable extent.—Structure 
and composition of shells of Arcella vulgaris and Cyphoderia margaritacea ; 
the former is composed not of hexagonal prisms, but of round pieces, lying 
on a structureless membrane, the latter consists of ellipsoid elements, so 
arranged as to appear hexagonal, Averintzev (9).—Structure of the calcium 
carbonate in the shells of Rhizopods (Foraminifera), Averintzev (11).— 
Inqierforate or porcellanous shell of Foraminifera, probably of conchite , 
Chapman (61).—An inner or “float” chamber inside the external or 
balloon chamber of Cymbalopora bulloides , Earland (95).—Comparison of 
mode of growth of test in Textidaria and Spiroplecta, Wright (418).— 
On the structure of the shells of various Orbitolinidce , Egger (98). 
Twinned-shells, “twins,” in Orbitolites duplex , full account, Rhumbler 
( 314).—These are to be distinguished from the “pairs” or couples which 
fuse when adult, (plastogamy) as in Patellina and Discorbina, and in which 
no further common additions to the shell are formed. In a “twin,” after 
the two individuals have united, subsequent shell-formation proceeds in 
either of two ways. The univalent mode is characterized by the fact that 
the “postjugally”-formed chambers are quite normal in arrangement, and 
the whole shell is only to be distinguished from that of a single individual, 
by the presence of two “ primitive discs ” instead of one, either in contact 
or separated by a few rows of “ priejugally ’’-formed chambers. This 
method results when young individuals (“ Erstlinge ”) unite, which are not 
yet forming complete rings of chambers, but only crescentic ones (“ Erst- 
lingskammern ”), and when they unite by the non-growing sides which 
have not yet commenced to secrete shell. When, on the other hand, the 
uniting individuals are apposed (and unite) by their growing sides (whether 
they are only forming crescentic or complete chambers), the bivalent mode 
results. This is distinguished by the presence of a raised wall (the 
“ Stauwand ”) which stands out from the plane of the shell, and marks the 
junction of the two halves; the cause being that the extending “proto¬ 
plasmic-masses ” mutually press against each other, and since the individuals 
are fixed, they cannot move apart, and therefore the new growth is forced 
upwards out of the common plane. Among other points brought out are 
(a) that the nuclei play no directing or controlling part in the process, but 
solely a material-supplying role is ascribed to them, and ( b ) that “ twins ” 
are formed indifferently by megalo- or micro-spheric forms or both. A 
lengthy explanation on developmental-mechanical grounds follows, Rhum¬ 
bler (314). 
The constancy of the “ homologous marginal angle ” of the polythalamous 
