36 MOEPHOLOGY OF 



Nemertines, &c., are usually found still suspended long after 

 most of the mud is precipitated. The water should then of 

 course be poured off and left to settle separately. The degree 

 to which any particular animals required may thus be easily 

 separated off from the rest is very great. The disadvantage of 

 such a method is that a certain number of larvae are sure to be 

 broken in the stirring necessary to effect suspension. I have 

 little doubt that the larvse which were observed free-swimming 

 earlier than stage F were thus liberated from the egg-shell. 



Preservation. — All my specimens of B. minutus were 

 obtained from Naples, being very kindly prepared for me by 

 Mr. Weldon with picric acid. 



Most of the larvae of B. Kowalevskii were placed for 

 less than a minute in corrosive sublimate sat. sol. two parts, 

 mixed with one part glacial acetic acid, washed with wa,ter and 

 successively passed through 30 per cent., 50 per cent., 70 per 

 cent., and 90 per cent, spirit. On the whole the results 

 given by this reagent were the best. The softer parts, however, 

 are best preserved in those specimens which were treated with 

 Perenyi's fluid one hour, then 90 per cent, spirit for twelve hours, 

 the 90 per cent, spirit being then changed. In the case of 

 adults preserved with Perenyi's fluid, the fluid was changed 

 once or twice. 



Osmic acid did not give good results, but probably this was 

 due to bad manipulation. The sections were cut in continuous 

 series with Caldwell's automatic microtome. 



