WAITE : ANTENNAL GLANDS IN HOMARUS AMERICANUS. 155 



most serviceable fixing reagents were, in the order named, the chrom- 

 osmo-picro-acetic mixture of vom Eath followed by pyroligneous acid, 

 Perenyi's fluid, and corrosive sublimate. For staining the material 

 fixed in Perenyi's fluid and corrosive sublimate, I have used Heidenhain's 

 iron hematoxylin, Delafield's hematoxylin, and Ehrlich's acetic acid-alum 

 hematoxylin. For a double stain orange G of Griibler after either of 

 the last two is of value. In general the carmines are not serviceable 

 in this connection, but picro-lithium carminate has afforded very good 

 results on the wall of the vesicle. 



Both surface preparations and serial sections were used in studying 

 embryos. The yolk was sometimes dissected away before sectioning, but 

 at other times it was sectioned with the embryo. The selection of the 

 killing agent to be used depends in a measure upon which of these two 

 methods is to be followed in sectioning. The specimens to be used for 

 examination by transmitted light must necessarily be separated from the 

 yolk. This was accomplished with fine needles and a small stream of 

 fluid from a pipette, the work being done under a dissecting microscope 

 and in alcohol of a lower grade than that in which the embryos had been 

 kept. This change in the grade of alcohol distends the egg membrane 

 so that it may easily be shelled off. The difficulty of the separation of 

 the yolk depends upon its friability and the age of the embryo. 



I have used for killing the following : (1) water, heated to boiling and 

 then quickly poured over the embryos ; (2) saturated aqueous solution 

 of corrosive sublimate, used either hot or cold ; (3) Perenyi's fluid ; 

 (4) Kleinenberg's picro-sulphuric mixture ; (5) Flemming's fluid, — 

 weaker mixture. Of these the hot water and the corrosive sublimate 

 treatment render the yolk granular and friable, so that it is easily sep- 

 arated from the embryo ; at the same time the yolk particles are so 

 loosely united that it is impracticable to section embryos with the yolk 

 attached. On the other hand, treatment with Perenyi's fluid makes the 

 yolk so firm and tough that it is almost impossible to dissect off the em- 

 bryo without serious injury to it. Treatment with picro-sulphuric mix- 

 ture, if of short duration (15 to 30 minutes), allows the yolk to be 

 removed in large masses, and completely, without injury. Longer treat- 

 ment (60 to 90 minutes) interferes with such removal, but solidifies the 

 yolk so that it can be easily sectioned with the embryo. The weaker 

 Flemming's fluid when used for a short time (20 to 30 minutes) gives 

 a tenacious rind enclosing the embryo, which is easily separable from 

 the coarsely granular central part of the yolk. A longer treatment (45 

 to 90 minutes) gives the best condition I have obtained for sectioning 



