144 PRINCIPLES OF EMBRYOLOGY 



The reaction between the testis and the ducts is not all in one direction, 

 since pigmented cells migrate out from the testis sheath on to the duct, 

 whose colouration is thus dependent on the kind of testis with which 

 they come in contact (Stem and Hadorn 1939). A more drastic effect of 

 the gonad on the associated duct occurs in females, where Pantelouris 

 (1955) has shown that the lateral branch of the oviduct does not elongate 

 unless it makes contact with the ovary. The ovary itself seems to be re- 

 latively independent in its growth, and can, though rather rarely, attain 

 its normal size even when not attached to any genital duct; this may 

 occur even in a male host. 



SUGGESTED READING 



Most of the original literature on experiments on embryos is in German; Seidel 1936, 

 1952a recommended; Haget 1953 is a fine original paper (in French); Wigglesworth 

 1947 summarises some of the Hterature; see Poulson 1945 for chromosomal control. 



For pupal stages, Hadorn 1948^, Waddington 1942(1. 



For pupation hormones, Williams 1951, Wigglesworth 1954, Seidel 1952^. 



