42 C. M. CHILD- AND E. V. M. Me KIE. 



the abnormal forms described represent differences in the dynamic 

 processes which are primarily purely quantii.itis e. The tem- 

 perature experiments illustrate this point very clearly. In a 

 given set of pieces higher temperatures increase the frequency of 

 normal, lower temperatures that of abnormal forms. The effect 

 of the anesthetics and the other external factors mentioned above 

 is probably also primarily quantitative. 



In these cases then different morphological characteristics 

 appear as the result of primarily quantitative changes in the 

 dynamic processes in the organism. This fact is of considerable 

 theoretical importance, since it can mean nothing else than that 

 form, structure, localization, number and even presence or ab- 

 sence of parts may be determined by purely quantitative changes 

 in external factors, i. e., by changes which alter primarily the 

 rate and not the character of the dynamic processes. 



Certain external characteristics of the head region of the ab- 

 normal forms, viz., the position and number of the eyes and 

 auricles, indicate that the cephalic ganglia of these forms must 

 show considerable departures from the norm. The question as 

 to how the form and structure of the central nervous system 

 may be altered by these quantitative changes in the dynamic 

 processes is one of interest from various points of view. The 

 data presented below give a partial answer to this question and 

 so form a contribution to our knowledge of the dynamics of 

 morphogenesis. 



The method used for obtaining the teratophthalmic and tera- 

 tomorphic forms described in this paper was that of cutting 

 pieces of a certain length, determined by previous experiments 

 of the senior author, from the middle region of the body of large, 

 well fed worms and allowing them to undergo regulation at about 

 20 C. This method was used merely because it is the simplest. 

 Teratophthalmic and teratomorphic heads develop on pieces of 

 greater length from the middle 1 region of the body, /'. e., the 

 posterior region of the first zooid (Child, 'i\<i, 'iu;) than from 

 any other region. This makes it possible to use relatively long 

 pieces and the preparation and handling of the material is there- 

 fore less difficult. Of course the abnormal heads can be obtained 

 from still longer pieces if regulation occurs at low teinper.n mv>. 



