Heredity in Protozoa 589 



(even if followed by increase in size), progeny would after a time 

 be produced that would have little resemblance to the parent. 



Thus it is evident that even in the Protozoa heredity is not a 

 mere result of subdivision. The question returns with force: 

 How does it happen that the localized structures of the progeny 

 are the same as those of the parent ? And are they the same in all 

 cases .^ Are they the same when the characteristics of the parent 

 have become changed during its lifetime as an individual .? 



We shall take up first the simplest and most marked charac- 

 teristics — new appendages, spines and the like; marked changes 

 in the form of parts of the body; all sorts of things that might be 

 characterized as mutations, abnormalities, monstrosities, etc. 

 We shall deal at the same time with mutilations. 



THE FATE OF NEW LOCALIZED STRUCTURES IN PARAMECIUM, WITH 

 OBSERVATIONS ON GROWTH AND REGULATION OF FORM IN 

 THIS INFUSORIAN 



By examination of dense cultures of Paramecium* many indi- 

 viduals were found which differed in certain respects from the 

 usual form or structure. Some had a short, truncate anterior 

 end; others a blunt or truncate posterior end in place of the sharp 

 tip; others were crooked or otherwise modified in form; others 

 showed angles, teeth or spines on various parts of the body. Many 

 of these were isolated and allowed to reproduce under observation, 

 so as to follow the fate of the peculiarity in question. 



The method of isolation and culture was essentially that de- 

 scribed by Calkins ('02). The individuals were placed separately 

 in the concavities of hollow-ground glass slides, in three or four 

 drops of hay infusion, which w^as changed either every day or 

 every two days. The animals were examined once or twice a day. 



I History of a Large New Appendage in Paramecium 



I shall first describe in detail a typical case of a new structure; 

 an individual that bore on its body a spine (Fig. 3). This case 

 is particularly instructive because the origin of the peculiarity 



*The animals studied had the characteristics usually attributed to Paramecium caudatum. The 

 question of distinguishing species will be taken up in later parts of this general investigation. 



