346 
SUMMARY OP CURRENT RESEARCHES RELATING TO 
Bergh emphasizes the fact that the nuclei and micronuclei of Infusorians 
in their division diifer from the nuclei of most cells in the persistence 
of the achromatic nuclear membrane, and in the absence of the proto- 
plasmic asters which have been observed even in Bhizopods. Where 
the membrane persists, it is evident that the achromatic filaments of 
the nuclear spindle cannot be of external cytoplasmic origin. 
Freshwater Heliozoa.’^ — Dr. E. Penard, in the second part of his 
memoir,| continues his account of Actinoplirys sol. Describing the 
liberation of an example which had been encysted during the winter, he 
says that in a cyst about to open there may be observed passing from the 
centre to the circumference a central grey matter ; this was mucilaginous 
and generally surrounded a circular spot, which, no doubt, represents the 
nucleus. More externally there is a wide ring of very small granulations, 
bordered by a zone of limpid plasma, without any contractile vesicle. 
This last zone is bounded by the internal cyst, which is delicate and 
extensile, and this again is separated from the external cyst by a muci- 
laginous material, similar to that which is found within it. The internal 
cyst always remains spherical, the outer generally elongates, and its 
ovoid form appears to be due to the powerful endosmosis which is going 
on. After a time it yields to the pressure within. The internal cyst 
distends, bursts, and is sometimes carried away. The mucilaginous 
liquid which surrounds the animal passes gradually to one pole, whence 
it slowly extends to the right and left, until at last it forms a zone of a 
clear grey limpid material, which soon becomes hollowed out by small 
vacuoles, and commences to form the ectosarc. Some of the neighbouring 
vacuoles increase in size, and by the loss of the partitions which divide 
them form a contractile vesicle. 
Some hours after the emergence of the animal, the pseudopodia are 
distinctly visible ; they exactly resemble the pseudopodia of Ciliophrys, a 
form to which the whole animal may now be compared. In most 
specimens a well-marked, central, spherical nucleus was seen, but in 
some cases it could not be detected. The vacuoles of the ectosarc con- 
tinue to exhibit differentiation, the contractile vesicle increases in size, 
the pseudopodia grow larger, and, in twenty-four hours, the young 
Actinophrys only differs from the adult by its smaller size. It is 
probable that, at this stage, it increases by fission. 
A detailed description is given of Acanthocystis pectinata sp. n. from 
Wiesbaden ; A. erinaceus and A. albida spp. nn. are more shortly discussed. 
CiliopJirys cserulea sp. n. is also fully described. Some notes on these 
forms have already appeared in another memoir.^ 
Myxosporidia.§ — M. P. Thelohan has recently made observations on 
the Myxosporidia. These interesting organisms consist essentially of a 
mass of protoplasm in which are formed at a certain period reproductive 
bodies or spores. They are distinguished from other Sporozoa by two 
principal characters, namely the structural complexity which their spores 
may attain, and the fact that the formation of these spores does not 
mark the termination of the evolutionary cycle of the organism, but 
* Arch, (le Biol., ix. (1889) pp. 419-72 (3 pis.). 
t See this Journal, ante^ p. 50, X this Journal, ante, p. 193. 
§ Annales do Microgr., ii. (1890) ])p. 193-213 (18 figs.). 
