394 Action of the Genetic Material 



of the mutant is a syndrome of pathological features which have to be 

 considered as a kind of mechanical consequence of a primary, early 

 embryonic damage. Bonnevie first analyzed a case in the mouse, 

 where, according to her interpretation, the mutant causes a hyper- 

 pressure of cerebrospinal fluid in the embryo; this leads to bleb forma- 

 tion, which later causes all kinds of damage to different tissues and 

 organs. Numerous cases of similar type have since been analyzed by 

 Griineberg, Dunn, Gluecksohn-Schoenheimer, Landauer, and others. 

 (See reviews in Goldschmidt, 1938fl; Griineberg, 1952Z?; Caspari, 

 1952; Gluecksohn-Waelsch, 1953.) It is obvious that these types do 

 not teach us much on interplay of genie action, and we shall, there- 

 fore, not go into further details. I drew this conclusion earlier when 

 discussing pleiotropic effects of multiple alleles (III 5 C Z?). 



A second, more informative type deals partly with the production 

 of a chemical substance, say a pigment, which affects most conspicu- 

 ously one process (e.g., production of eye color), but simultaneously 

 acts upon other pigmentation processes at other places and, some- 

 times, in a qualitatively different way. A well-known example is the 

 effect of light eye color (also body color) mutants of Drosophila 

 upon the hue of pigmentation of gonads and Malpighian tubules (see 

 Brehme and Demerec, 1942). We might call this type "pattern pleio- 

 tropy." Caspari (1952) has drawn attention to the fact that even 

 Mendel knew an example, namely, a mutant in the sweet pea, which 

 influenced at the same time the pigment in the seed coat, in the flower, 

 and in the axils of the leaves. Some similar cases have been thoroughly 

 studied in the work on biochemical genetics of the Kiihn and Beadle 

 schools. For example, in the flour moth (Caspari, 1933) the wild type 

 produces a diffusible substance which is needed for the pigmentation 

 of eyes, testes, and larval hypodermis. In the mutant this substance 

 is not formed (details elucidated in transplantation experiments). 

 The substance is kynurenine (also in the parallel Drosophila work of 

 Beadle and Ephrussi, 1936), a precursor for all these pigments. 



To this group of "pattern pleiotropy" belong also a number of 

 morphological pleiotropies, in which it is impossible at present to 

 specify a definite genie product. Such, for example, are cases in which 

 a similar type of effect appears in different organs. The mutant podop- 

 tera (in Drosafjliila) affects primarily the wing, which grows into a 

 leglike appendage. Simultaneously, the legs are frequently abnormal 

 in different ways (details in Goldschmidt, Hannah, and Pitemick, 

 1951). Both effects are, in a general way, interferences with growth 



