840 SUMMARY OF CURRENT RESEARCHES RELATING TO 



forming the V's being very fine. (D is dirt matter on the slide con- 

 cealing portions of the membrane.) 



From the above and other observations I would suggest that the 

 movement of some diatoms is carried out by means of an undulating 

 and extensible membrane with radiating arms. It would account 

 well for movements as yet unexplainable, as for instance, when a 

 diatom is fixed by one extremity, and has the other end pushed aside 

 by another diatom. When the force so exerted is suddenly removed, 

 the first diatom springs back into the first position, like a bent spring 

 released, as if acting by muscular power. 



Having cracked the cover-glass, I am unable now to use an 

 immersion lens, but what I have mentioned is still visible with a 

 good dry ^." 



Mr, H. Mills has also detected* in Stephanodiscus Niagara 

 fine threads twice the diameter of the frustule, as Professor H. L. 

 Smith had previously done in the same object. 



Symbiosis of Animals and Algse.t — In pursuance of his investi- 

 gations on the symbiosis of certain algae with the lower animals, 

 G. Eutz states that he has been able to detect in the pseudo-chloro- 

 phyll-bodies of the infusoria two clear spots which must be regarded 

 as contractile vacuoles. The view previously brought forward that 

 their presence in animal organisms is due to their being taken in 

 with their food is confirmed by the fact that they are scarcely ever 

 found except in the mature individual. Almost the only exception to 

 this is the case of Hydra viridis, where they occur in the ova. 



With regard to the designation of these organisms as parasites, 

 the term can only be applied to them in a very wide sense, since they 

 can live if removed from their host, which is not the case with true 

 parasites. 



Vampyrella and its Allies.;]; — J. Klein has continued his obser- 

 vations on the interesting genus Vampyrella,§ and furnishes many 

 further details respecting the development of the different species. 

 In V. variabilis, he observed that the zoospores sometimes conjugate 

 into a plasmodium even before their escape from the cyst. If the 

 zoospores fail to conjugate, after a considerable time they will put 

 out one or two long slender pseudopodia instead of the much larger 

 number of shorter ones, and by this means effect conjugation with 

 other zoospores. 



V. vorax is parasitic upon diatoms, as for example Synedra ; and 

 in this species the conjugation of the zoospores may be very well 

 observed. They consume the greater part of the contents of the 

 diatom-shell. V. pendula occurs on several species of (Edogonium, 

 and exhibits essentially the same phenomena as the preceding species. 

 V. inermis resembles pendula in being parasitic on (Edogonium, and 



* Amer. Mon. Micr. Journ., iii. (1882) pp. 8-9. 



t Biol. Oentralbl., ii. (1882) pp. 451-64. Cf. this Journal, ante, pp. 241, 542. 



X Bot. Centralbl., xi. (1882) pp. 187-215, 247-64 (4 pis.). 



§ See this Journal, ante, p. 544. 



