80 EMBRYOLOGY OF INSECTS AND MYRJAPODS 



Too much theorizing has ah'eady been done on insufficient data. Pend- 

 ing the accumulation of more information, especially with reference to the 

 development and fate of the primary and secondary yolk cells, of the 

 yolk cell and ental membranes, and of the yolk cells as provisional mid- 

 gut epithelium, we deem it wise to withhold judgment. 



In concluding this topic we cannot refrain from quoting a paragraph 

 from a recent paper by Dr. Albert Miller (1940), which contains a sug- 

 gestion that we are most inclined to support: 



Perhaps, after all, only the vitellophags may be justly homologized with the 

 entoderm of other invertebrates, using the term "entoderm" in a strictly embryo- 

 logical sense, rather than in a functional or anatomical sense (as it is when the 

 mid-gut tissue is called entodermal by virtue of its definitive position) . To extend 

 the embryological concept of the term further, in forms refractory to its applica- 

 tion, subjects the germ-layer theory to so severe a strain that it loses its essential 

 characters if not its entire meaning. In our preoccupation with terms there 

 is danger of losing sight of the true nature of living matter — its remarkable 

 adaptability; adaptability that may invalidate our best intentioned attempts to 

 pigeonhole its other manifestations. 



References 



Bobretsky (1878), Braem (1895), Brass (1883), Blitschli (1888), Cholodkowsky 

 (1888), Deegener (1900), Eastham (19306), Escherich (1900, 1901), Ganin (1874), 

 Graber (1878), Heider (1885, 1897), Henson (1932), Hertwig (1880), Heymons 

 (1894a, 1897), Hirschler (1907a, 1909a), Inkmann (1933), Jentsch (1936), Jordan 

 (1888), Korotneff (1894), Krause (1938a), Lecaillon (1897a,6, 1907), Mansour (1927, 

 1930), Nelson (1911), Nusbaum and Fulinski (1906, 1909), Rabito (1897), Richards 

 (1932), Rizzi (1912), Schwangart (1904, 1907), Schwartze (1899), Sehl (1931), Snod- 

 grass (1933, 1935a), Stecker (1877), Strindberg (1913o, 1914a, 19156), Stuart (1935), 

 Tchang (1929), Thomas (1936), Tichomiroff (1890a, 1892), Tichomirowa (1890a), 

 Tschuproff (1903), Will (18886), Wagner (1894), Zograf (1882). See also the list of 

 general works cited in Chap. II. The paper by Eastham (19306) is a comprehensive 

 summary. 



