ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 179 



Protozoa. 



New Heliozoon.* — H. R. Hoogenraad describes Frmzelina minium 

 sp. n. from fresh-water pools in Holland. He contrasts it with Penard's 

 F. reniformis from the Lake of Geneva, and gives the following extended 

 definition of the genus : — Shell hemispherical or more than hemispherical, 

 slightly compressed antero-posteriorly and vertically, thin, glassy, trans- 

 parent, more or less thickly covered with foreign particles ; the plasma 

 has an elliptical or kidney-like shape, with thread-like, often forked 

 pseudopodia. The genus is readily distinguished by the shape of the 

 shell from the nearly allied Pseudodifflugia. 



Conjugation in Anoplophrya.f — B. Collin describes the details of 

 the conjugation in Anoplophrya branchiarum Stein (= A. circidans 

 Balbiani), the well-known astomatous parasite of the blood of Gam- 

 marus pulex. There are two micronuclear maturation mitoses, and a 

 third division forms the pronuclei. The migration of one of the pro- 

 nuclei in conjugation is described. A study of the behaviour of the 

 macronuclei confirms the interesting observation of Schneider that there 

 is an exchange of half of the macronuclei between the conjugates. 



Notes on Suctoria4 — B. Collin has some notes on Dendrosomides 

 paguri Collin, pointing out that the vermiform individuals, produced by 

 the tentaculate (trifurcate) types by external budding, can transform 

 themselves into trifurcate types. The dimorphism is only apparent. 

 In Podophrya fixa 0. F. Miiller there are two forms of encystation — for 

 division and for rest. What has been called transverse division in 

 Podophrya is budding, with a change of axis. Within the cyst, Collin 

 observed what looked like division into two and then into four, but it is 

 really budding. The products pass out as ciliated or tentaculate forms. 

 A budding which looks deceptively like division occurs in.parasitic forms 

 of Sphserophrya. 



Life-cycle of Paramecium^ — L. L. Woodruff finds that the proto- 

 plasm of these organisms, when subjected to a comparatively constant 

 culture medium, passes through long cyclical changes in vitality which 

 finally result in the death of the organism. The protoplasm may be 

 "rejuvenated" by suitable changes in the culture medium (stimuli) at 

 critical points in the cycle, and thus be enabled to resume active repro- 

 duction for a longer period. The essential fact brought out by this 

 study is that the protoplasm of the individual Paramecium isolated 

 over two years ago to start the culture has had the potential to divide 

 (so far) over one thousand two hundred and thirty times at an average 

 rate of more than three divisions every two days, and the representatives 

 of the untold millions of its progeny which are still in captivity give 

 every indication of being in as normal physiological and morphological 

 condition as their ancestor. This suggests that when the protoplasm is 

 constantly subjected to a suitable varied environment the cycle may be 

 greatly prolonged and probably entirely eliminated — the fluctuations in 

 vitality not transcending the rhythm. 



* Tijdschr. Nedorland. Dierk. Ver., xi. (1909) pp. 61-70 (1 pi.), 

 t Arch. Zool. Exper., i. ser. 5 (1909) pp. 345-87 (2 pis. and 2 figs.). 

 X Comptes Rendus, cxlix. (1909) pp. 1407-8. 

 § Biol. Bulletin, xvii. (1909) pp. 287-308 (5 figs.). 



