3 1 6 Canadian Record of Science. 



NOTES. 



Ophiothrix fragilis is one of the most common British 

 Ophiurids. Some years ago when at Plymouth, England, I 

 succeeded in obtaining a large number of the larvae in all 

 stages of development, and I have been engaged for the last 

 two years in working out their structure. The adult, like all 

 Echinodermata, is radially symmetrical, but the larva is bilater- 

 ally symmetrical, more markedly so than any other Echinoderm 

 larva which I have examined. Further, it shows during its 

 development, traces of a metameric repetition of parts such as 

 is found in bilaterally symmetrical animals like Annelida. This 

 metamerism is exhibited in the ccelom or body-cavity vesicle. 

 This is budded off from the apex of the gut when the larva is 

 2 days old, and it immediately divides into right and left halves. 

 At the age of eight days, each half divides into a posterior 

 vesicle lying at the side of the cesophegus. At the age of fifteen 

 days each of the anterior vesicles buds off a thick walled pos- 

 terior portion. The left one becomes the hydrocele or rudiment 

 of the water-vascular system of the adult, whilst the right loses 

 its cavity and becomes a solid mass of cells whose further fate 

 I am engaged in tracing. 



E. W. MacBride. 

 Zoological Laboratory, 



McGill University, April, 1905. 



The Marine Biological Station of Canada will open 

 for the summer during the month of May, under the Di- 

 rectorship of Prof. E. E. Prince, assisted by Dr. Stafford 

 who will be in immediate charge. The Laboratory will be 

 located at Gaspe where investigations will be continued with 

 respect to the problems relating to fish culture, which have 

 been dealt with at other stations during the last five years. 



