438 R. M. PACE. 



is from April to June, while in July and August larvfe in 

 advanced stages are still abundant, but at this time young 

 stages and ova are rare. On the other hand, even in March 

 and April, colonies may be found which contain only mature 

 larvae. It should be stated that in any one colony the 

 majority of the larvae are at approximately the same stage of 

 development. 



Flustrella hispida will readily live in standing water 

 for from one to five days according to the time of year, while 

 in running water it has been kept in good condition for over 

 a week,^ but it is best whenever practicable to work with quite 

 fresh material, as the larvse appear less healthy in colonies 

 which have been kept even a few days. 



Methods. — The work has been done partly by the study 

 of entire larvae and partly by means of sections. The larvae 

 were examined both in the living state and after fixation. 

 For the latter purpose lai'ge numbers of eggs and larvae were 

 removed from the colonies and preserved and in addition 

 portions of colonies were fixed entire in order to study the 

 larvae in situ. 



Fixing Reagents. — The preservatives used were : — 



(1) Cold saturated solution of corrosive sublimate, with the 

 addition of 5 per cent, glacial acetic acid. 



(2) 100 parts 5 per cent, chromic acid, with five drops of 

 glacial acetic acid. 



(3) Flemming's solution. 



(4) Hermann's solution. 



(5) Dr. Allen's chromo-nitro-osmic acid mixture. 



(6) Acetic alcohol containing sublimate to saturation. 



(7) Kleinenberg's solution. 



Preserving Larvae in situ. — For preserving larvae in 

 situ it has been found best to cut the colonies with the 

 seaweed on which they are growing into small portions, and 

 to immerse these in the fixing solution for some time to allow 



* At Millport, owing to the exceptional purity of the water, there appears 

 to be no diflBculty in keeping Flustrella alive in the tanks for a quite in- 

 definite period. — R. M. P. 



