J 50 HIROSHT OHSIIIMA 



organ-forming substance out of which the hydrocoele arises — 

 and that this organ-forming substance gives rise to 

 both hydrocoeles. 



The results which I obtained in 1917 I was able to obtain 

 under precisely similar conditions in 1919. Dr. Ohshima's 

 failure to obtain them in 1920 may, I think, be attributed to 

 several causes. I stated that for success several conditions 

 were necessary, one of which was a vigorous culture of the 

 diatom Nitzschia. For some unknown reason this was exces- 

 sively difficult to obtain in 1920. Again and again our cultures 

 died off and the larvae were checked in their development. 

 Dr. Ohshima obtained a few ' doubles ' both in the control and 

 the ' treated ' culture which were started in May, and a few more 

 doubles in the control culture started in June. But the May 

 cultures were not obtained from satisfactory females : they 

 were obtained from masses of eggs in which only a small pro- 

 portion developed, and they could not be described as vigorous 

 cultures or likely to show a proper reaction to stimulation. 

 The June cultures were vigorous, but, owing to the failure of 

 the Nitzschia culture, the ' treated ' culture died off com- 

 pletely, and the ' control ' culture was for weeks in a condition 

 of checked and stunted growth and only recovered later when 

 the Nitzschia finally re-established itself. In a word Dr. Ohshima 

 obtained his specimens with a right hydrocoele through the 

 checking of the growth of the normal left one by starvation, 

 whilst I obtained mine in 1917 and 1919 by stimulating the 

 larvae in their early growth by the action of hypertonic sea- 

 water. E. W. MacBride. 



