360 A. RICHARDS. 



case fertilization was at n : oo, 50 per cent, of the embryos in the 

 alkaline sea water were swimming at 4 : 20, although all were 

 motionless in the normal, and the first signs of movement in the 

 latter were seen at 4 : 40. Loeb showed that the effects of the 

 alkali were not simply upon ciliary movement, but also upon the 

 development of the eggs themselves, for the next morning after 

 such an experiment as the one just described the embryos in the 

 alkaline solution would be in the plntcus, for example, and the 

 normals in the round gastrula stage. And the alkali produced a 

 difference not only in acceleration of the rate, but also an increase 

 in the size of the plutei. 



A similar action to that of the hydroxyl-ions was obtained by 

 Mathews by the employment of pilocarpine hydrochlorate on 

 Astcrias larvae. He found that the pilocarpine hastens the devel- 

 opment and gives rise to abnormally large embryos, while atropine 

 hindered the development and gave rise to dwarf embryos. Both 

 of these drugs act directly upon the animal cells, and the nature of 

 their action suggests that the atropine inhibits the oxidations taking 

 place in those cells, while the pilocarpine increases those oxida- 

 tions. 



All of these agencies have the effect of accelerating the rate of 

 cell division. In most cases the effect is only a slight one, but 

 some of the stimulants are marked in their efficiency. However, 

 even slight effects are significant if they are constant, and a careful 

 analysis of the means by which acceleration even of slight amount 

 may be produced will doubtless give additional light on the mech- 

 anism by which cell division is brought about. 



EXPERIMENTS WITH Haminea EGGS. 



During the summer of 1921 the writer studied the effect of a 

 number of accelerants upon the cleavage of the eggs of the opistho- 

 branch Haininca rircsccns (Sowerby) at the laboratory of the 

 Scripps Institution for Biological Research at La Jolla, California. 

 The eggs of this animal are particularly favorable for experiments 

 in which it is desired to test the effect of some special factor while 

 leaving the egg in an environment that is normal in all respects 

 except that investigated. The animals were brought into the labo- 

 ratory and kept in a dish of running sea water supplied with a 



