460 



THE AMERICAN NATURALIST 



[Vol. LIV 



In order to explain the case reported by Whitman an entirely 

 new and unsupported behavior of the lethal factor is hypothe- 

 sized. This consists in a supposition that females possessing two 

 does of the lethal die. Inasmuch as a female with two doses of 

 a sex-linked lethal could not be formed except by mutation, pro- 

 vided the relations observed in Drosophila hold true, the pres- 

 ence of a sex-linked lethal factor of the accepted type does not 

 appear to be strongly supported. In the case of the rats a 

 simple statement of a difference in reciprocal crosses is the sole 

 evidence. In this case no lethal action is apparently involved; 

 but sex-linkage might possibly account for the result. Until 

 actual experimental evidence on this matter is available, how- 

 ever, it seems as though it was not sufficiently definite to be con- 

 sidered as having previously established the existence of sex- 

 linkage in rodents. 



C. C. Little 



CONCERNING THE FOSSILIZATION OF BLOOD 

 CORPUSCLES 



Recently, while studying a series of microscopic preparations 

 of fossil material in connection with paleopathology, I observed 

 in sections of a dinosaur bone (possibly Apatosaurus) which I 

 had collected in the Como beds of Wyoming in 1906, some ovoid 

 bodies, arranged around the periphery of vascular spaces and 

 Haversian canals, which looked remarkably like blood corpuscles. 

 Close scrutiny of the available material, however, did not satisfy 

 me that the objects might not be the products or by-products 

 of incomplete crystallization. The majority of the bodies had 

 the size and shape of modern reptilian erythrocytes ; the nucleus 

 of course not being evident, since only the outward form of the 

 corpuscle was to be seen. Other bodies, apparently similar, 

 were irregular in shape and hard to distinguish structurally 

 from the regular bodies. These latter, however, may be masses 

 composed of several corpuscles which had become agglutinated. 



Not being satisfied with the results of my observations, I should 

 not have published anything about it had I not seen in a memoir 

 by Seitz 1 a description of similar bodies in sections of normal 



i Adolf Leo Ludwig Seitz, 1907, * ' Vergleichenden Studien liber den raikro- 

 akopischen Knochenbau fossiler und rezenter Reptilien und dessen Bedeu- 

 tung fur das Wachstum und TJmbildung des Knochengewebes im allge- 

 meinen," Nova Ada. Abh. der Kaiserl. Leop.-Carol. Peutschen AJcad. der 

 Naturforscher. Halle, Bd. LXXXVTJ, No. 2, 329-330, Tab. XXI, Fig. 61, 



