HISTORICAL REVIEW 



The first recorded observations on the embryology of the 

 honey bee are those of the late Professor Weismann, transmitted 

 by him in a letter to the famous Russian investigator, Prof. Elias 

 Mecznikow (Metschnikoff), who published these in his Em- 

 bryologishe Studien an Insekten (1866, pp. 489-490). Weis- 

 mann's statement is as follows : "In the bee a germ layer is 

 formed, which however does not become part of the embryo, 

 but which soon separates from the yolk and becomes an amnion- 

 like envelope. This at first remains in connection with the yolk 

 at the poles, and becomes entirely free only at a later period, 

 when the yolk has become transformed to the true embryo. It 

 is clear that this amnion-like envelope is the embryo, from which 

 there then arises by metagenesis that which we term the bee 

 embryo." These brief and remarkable observations were soon 

 followed by two important papers. The first of these was that 

 of Dr. Otto Biitschli, published in 1870, entitled "Zur Entwick- 

 lungsgeschichte der Biene." This paper comprises 45 (8z/o) 

 pages of text and four double plates. Biitschli studied only 

 the living eggs. The features of the development visible from 

 the exterior were quite accurately described and figured, but the 

 observations of this noted zoologist were naturally limited by 

 his method, and while he succeeded in discerning correctly the 

 origin and development of certain internal parts, such as the 

 tracheal system, a systematic and detailed account of the origin 

 of the germ layers and of the details of the organogeny was in 

 the nature of the case impossible. 



In the next year (1871) appeared an extended memoir by 

 the Russian embryologist Kowalevski, entitled "Embryologische 

 Studien iiber Wiirmern und Arthropoden." It comprises seventy 

 pages of text (4to) illustrated by twelve plates. This paper is 

 a veritable landmark in the domain of insect embryology. Kow- 

 alevski made use of a method new at that time, namely that of 

 cutting sections of the tissue, previously fixed and embedded in 



