NOTES ON THE REAhING OF ECHINOID LARVAE. 97 



and in that year there were great quantities of Halosphnera in the 

 water. I did not realise until late in 1899 that such a quantity of 

 water should be added each day ; had I done so earlier, ray success 

 might have been even greater than it was. The fact was brought to 

 my attention by observing that plutei went on living in an apparently 

 healthy manner, but that the rudiment of the echinus within them 

 either failed to increase in size, or was actually resorbed. 



It appears to me likely that the difficulty experienced in rearing 

 many marine larvse is largely that of finding food ; for there appears to 

 be no reason why they should require more oxygen per day than do the 

 yolky eggs of other species in which development is direct, and goes on 

 with great rapidity. 



In conclusion, I have to express my gratitude to my friends Mr. E. J. 

 Allen, the Director of the Station, and Mr. E. T. Browne, of University 

 College, London, for much assistance and advice. 



Zooi-ofiiCAL Ladoratouy, McGili. Univei'.sity, 

 MoxTiiEAL, October 9. 1899. 



NEW SEIUES. — -VOL. A'l. XO. 1. 



