94 NOTES AND MEMOBANDA. 



however, only wlien two individuals are present ; so tliat a mutual 

 action, independent of actual contact, is evidently exerted. This pro- 

 cess the writer compares to the mode of fertilization in Floridece,, where 

 cells far removed from the trichogyne, to which alone the fertilizing 

 influence of the spermatia is ajiplied, are stimulated to a new and 

 vigorous growth by the impregnation ; and to the process which 

 obtains in Phanerogams, where the protoplasms of the male and female 

 cells arc sejiarated from one another by the cell- wall of the pollen 

 tube. In both these cases, however, one of the sexual cells only (the 

 female cell) undergoes further growth, the other or male cell disap- 

 pearing ; while in the desmids in question, the action of the two cells 

 is mutual. 



The writer then defines sexuality as the action of two or more cells 

 on one another, by means of which a new process of growth, in one or 

 all of these cells, is set up, and the sexual action consists in the stimu- 

 lation of the sexual cells to a new and peculiar growth, such growth 

 being impossible without that stimulation. 



Microscopical Injection of Molluscs. — Dr. W. Flemming has 

 originated * a method of killing molluscs for purposes of fine injection, 

 which he has found very successful. He recommends freezing the 

 animal by means of a mixture of ice and salt, and placing it, when 

 frozen, in tepid water for a quarter of an hour ; it is then found to be 

 dead and stiif with the valves gajiing, and the muscles no longer offer any 

 opposition to the passage of the injection. Unlike many other methods 

 of killing, this freezing process produces no injury to the tissues. 



In injecting Lamellibranchs from the heart, there is great danger 

 of extravasation. To obviate this difficulty, Flemming recommends 

 wiping the surface carefully after insertion of the cannula, and then 

 covering the animal with a soft paste of plaster of Paris. If this is 

 done successfully, the cannula is firmly fixed in its place, and extrava- 

 sation from the cut surfaces of the adductors and other dangerous 

 places is effectually prevented. 



Parasitism amongst Infusoria.— Dr. J. van Eeesf has observed 

 three cases of parasitism in this group, two of which are new, while 

 in the case of the third his account differs somewhat from that of its 

 discoverer. 



1. Vorticella microstoma. — The curious parasite Endosplicera having 

 this sj)ecies for its host, was first described by Engelmann in the first 

 volume of the ' Morphologisches Jahrbuch.' Endosplicera is a peri- 

 trichous infusor found in the interior of the body of Vorticella, where 

 it multiplies by budding, the buds making their way out of the body 

 of their host and swimming freely in the water for a longer or shorter 

 time, imtil another Vorticella is met with. Engelmann stated that 

 the parasite is then taken into the body of its Lost by the ciliary 

 current of the latter, but, according to Eees, it fixes itself about half- 

 way between the proximal and distal ends of the Vorticella's body, 

 into which it gradually penetrates, still showing its nucleus and con- 



* ' Archiv f. Mik. Auat.,' vol. xv. p. 252. 

 t ' Zeitsch. f. wiss. Zool.,' vol. xxxi. p. 473. 



