CENTRAL NERVOUS SYSTEM IN PLANARIA. 4! 



produced from any region of tin- planarian body and from piece- 

 of any size above a certain minimum, which varies with region 

 ol tin- b'ldy, physiological condition, age. nutrition and external 

 condition-;. A regional factor does, however, exi-t Child. 'ii</>: 

 in piece- of a given length the more posterior the level within a 

 -ingle /ooid. the greater the frequency of the abnormal form-. 

 Thu- far it has been possible to control experimentally the 

 prodnciion of teratophthalmic and teratomorphic as \\e11 as 

 anophthalmic and headless forms (Child. 'lie) in the t'o'louing 

 ways first, under standard conditions of t-ni|)erature. ninritit>n. 

 eti . pi < es above a certain length with anterior end- at a certain 

 le\e| ,,| ili,- l.odv \vill produce normal whole-, -horter piece- will 

 prodiKe teratophthalmic forms and still shorter piece- terato- 

 morphic. .m< iphthalmic and headless form- a- the length de- 

 : 'Hid. in pieces of a given length from a gi\en \-< -ion. 

 under iinitinn conditions of temperature, nutrition, etc.. -tinml.t- 

 tion to motor activity increases the frequen<\ ol normal anim.t 1 -. 

 uliile lai 1: ot stimulation increases the frequency of teratophth.il- 

 mic, teratomorphic, anophthalmic and he, idle-- form-. Third, 

 in pie. es ol i Jvc-n length from a given re-ion of anim.il- of the 

 ie -j/e the frequency of abnormal and tioim.il form- varies 

 \\itli difference* in physiological age (C'hi'd. ' I I ; " and \\ith dif- 

 n. ex in nut rit ion. Fourth, in pieces ot -^i\ en length Irom a 

 given ie. ion of animals of the same size and a- ne.irK a- poi bit- 

 in the -ame | >li\ siological condition a \.uietv of external facior-. 

 -uch as lo\\ teni|)eratiire, metabolic produ. i- in tin water, dilute 

 al<-ohol. I'ther, chloretone, potassium c\anide. etc., \\ill increase 

 the fre(|uenc\ of abnormal forms and it i- po--ible to control to 

 a certain extent the type of abnormal form, both through the 

 length of the piece and the intensity of the experimental factor. 

 ( >n the other hand, the frequency of normal form- in a -i\ en --t 

 of pieces can be increased by good nutrition, by high temperature 

 and probably also by certain stimulating drug-, 'luni-h as re- 

 gard- the-e la-t the results are complicated l.v the fact that in 

 main ca-e- the stimulating effect of drugs is of relatively -h..n 

 duration and i- fo!io\\ed by a depression. 



Hut \\hate\ er may be the results of more ex: ended experiment, 

 the fact- alrcadv e-tabli-hed demon-irate that the normal and 



