PROTOZOA AND INVIOUTEBRATE EGGS 



309 



conclusion is justified. As has been pointed out in a preceding paragraph, 

 a nucleoprotein-type action spectrum does not, by itself, indicate that the 

 nucleus is involved. Effects upon cytoplasmic nucleic acids are just as 

 possible. Moreover, the duration of an effect through a number of divi- 

 sions before recovery does not necessarily mean that the effect is nuclear. 

 Long-lasting cytoplasmic effects are also possible. It can only be con- 

 cluded that there is no critical evidence on the localization of the changes 

 leading to division delay in Paramecium. 



100-1 



80- 



60- 



40- 



20- 



2200 



2400 



2600 

 WAVE LENGTH. A. 



2800 



3000 



Fig. 8-5. Action spectra for retardation of cell division in well-fed paramecia, modified 

 from Giese (1945b), and from Kimball, Geckler, and Gaither (1952). Open circle = 

 time to third division (Giese) — Paramecium, well-fed. Solid circle = time to sLxth 

 division (Kimball, Geckler, and Gaither) — Paramecium, well-fed. 



INHERITED EFFECTS 



There have been scattered reports of mutation induction in inverte- 

 brates, other than insects, but such studies add nothing basically new to 

 the studies of mutation which are to be considered elsewhere in this series. 

 This section will be concerned almost entirely with the protozoa. For 

 this group a rather different point of view from that in classical mutation 

 investigations must be taken where inherited effects are concerned. 

 Work reviewed by Sonneborn (1947, 1949) has made it clear that watch 

 must be kept for kinds of inherited differences which are not dependent on 



