440 R. M. PACE. 



Preparation of Sections. — Sections were made both 

 of the isolated larvae and of portions of colonies containing 

 larvae. The watch-glass method of imbedding was found tho 

 most convenient, especially when dealing with isolated larvae. 

 Groups of from twenty to thirty isolated larva) were imbedded 

 on masse and sectioned, sections thus being obtained in a 

 variety of planes. The larva at nearly all stages has a definite 

 axis, which renders it possible to orientate it and so to obtain 

 sections in any desired plane. To serve as a guide in deter- 

 mining in which direction uuorientated larvae had been sec- 

 tioned, a set of standard sections was prepared by carefully 

 orientating single larvae which had been first studied entire. 



Finally, portions of colonies were imbedded and cut with 

 the larvEe in situ. To insure thorough impregnation, it was 

 found best to soak the material in xylol for about a week, 

 then to leave it in a mixture of xylol and paraffin for about 

 six hours in a warm place, such as the tray of the water-bath, 

 and finally to transfer to pure paraffin for about an hour. In 

 cutting such material great difficulty has been experienced 

 owing to the fact that the larvae lie close under the front wall 

 of the colony : this wall, being beset with chitinous spines, 

 renders it difficult to imbed and to cut in such a manner that 

 the razor encounters none of the spines when passing through 

 the larvfB, since the chitin is sufficiently hard to notch the 

 razor, thereby of course causing the section to tear. This 

 difficulty is less marked in the case of transverse than of 

 longitudinal sections. 



Staining. — The most useful stain for sections appears to 

 be Heidenhain's iron htematoxylin, followed by eosin dissolved 

 in 90 per cent, alcohol. By this treatment the structure of 

 the yolk nucleus and of all nuclear bodies is brought out very 

 clearly. Borax carmine and safranin have given good results, 

 and double staining with methyl blue and eosin has also been 

 found useful. Mayer's alcoholic cochineal, picronigrosin, 

 haematoxylin with a few drops of Kleincnbcrg's solution, 

 haematoxylin and methyl orange liavc also been utilised; 

 Mayer's mucicarmine was used for the detection of mucus. 



