I 1 8- PSYCHE [June 



STUDIES FOR STUDENTS.— III. ELEMENTARY STUDIES IN 

 INSECT HISTOLOGY. 



BY VERNON L. KELLOGG, STANFORD UNIVERSITY, CALIFORNIA. 



For the study of the anatomy, or histology, of insect tissues, the laboratory or 

 working room must have a certain minimum of equipment and the student a cer- 

 tain elementary training in histologic method or technic. By the technic of insect 

 histology is meant the particular methods of killing, fixing, hardening, clearing, 

 infiltrating and imbedding, sectioning, staining, and mounting, so that the various 

 body tissues may be available for examination and study under considerable micro- 

 scopic magnification. With the methods of manipulation acquired by instruction 

 and experience, the actual study of the histologic characteristics of the various 

 particular tissues and organs of the insect body can be undertaken. The tissues 

 should be studied first, for almost any organ comprises in its intimate make-up 

 several distinct tissues or kinds of cellular aggregates. In this paper I purpose 

 giving, first, a brief account of a generally applicable course of procedure in prepar- 

 ing insect tissues for histologic study, and then a series of brief directions and 

 hints for the recognition and study of the various typical or normal insect tissues, 

 and finally similar directions and suggestions for the study of the fine anatomy of 

 the principal insect body-organs. 



As in Studies I (Psyche, vol. 9, p. 207) on insect anatomy and Studies II 

 {Loc. cit., p. 246) on the development of the histoblasts of wings and legs, the giant 

 crane-fiy Holonisia rubiginosa was used for specific subject, the same insect species 

 will be used as principal subject of this paper. But it is plain, that the similar 

 study of any other insect may be based on the study here outlined of this particu- 

 lar one. 



Histologic Technic. Killing and fixing. — The chitinized cuticula of the 

 insect body is nearly impervious to fixing fluids, so that for quick killing and fixing 

 of the tissues, heat is, in most cases, the best killing agent. Tissues that have 

 been dissected out from the body of a live (chloroformed) specimen may be fixed 

 without heat in any of the usual fluids. To kill and fix the whole body of insects, 

 drop specimens alive into boiling water; leave them in this but a moment or two, 

 /. e., until the body is rigid, then transfer to 30% alcohol. While here puncture 

 the body wall with a needle, scalpel, or fine scissors in several places, not cutting 

 deeply nor making the wound in the dorso-ventral median longitudinal plane of 

 the body. Leave in ^o^/c alcohol three hours; then transfer to 5 o'}^, alcohol for 

 three hours, then to 75% alcohol for from six to twelve hours, then to 85% alcohol 



