1914] Sharp: Diplodinium ecaudatum 101 



CONCLUSIONS 



1. One result of the present study has been the discovery of three 

 new forms of Diplodinium ecaudatum, namely forma bicaudatum 

 (two posterior spines), forma tricaudatum (three posterior spines), 

 and forma quadricaudatum (four posterior spines). These three 

 forms, together with D. caudatum Fiorentini (one posterior spine), 

 and D. cattanei Fiorentini (five posterior spines) because of their 

 structural similarity have been assigned to the species ecaudatum (no 

 posterior spines). 



2. Diplodinium ecaudatum, therefore, consists of a series of six 

 forms ranging from D. ecaudatum, without posterior spines, up to 

 D. cattanei, a form with five posterior spines. No other structural 

 characteristics distinguish these forms from each other. 



3. The reasons for assigning Diplodinium caudatum and the forms 

 bicaudatum, tricaudatum, quadricaudatum, and cattanei to the 

 species D. ecaudatum are as follows: First, with the exception 

 of the presence or absence of the spines, the dimensions and structures 

 of all these forms are practically identical. Second, the series of 

 spines from D. e. forma ecaudatum, without spines, up to D. e. forma 

 cattanei, with five spines, is complete. Third, with the exception 

 of the primary spine, spines of all sizes are to be found, ranging from 

 mere nodules up to spines which are equal to one-third of the entire 

 length of the body. 



4. The reasons why each of these types of this organism has been 

 designated as a "forma" according to the number of spines present 

 are as follows : 



First In every case of division observed animals with a certain 

 number of spines gave rise to two daughter animals, each of which 

 was provided with the original number of spines. Attention is called 

 to the fact, however, that none of these cases of division, so far as the 

 evidence is at hand, followed at once after conjugation, and that it is 

 possible that division immediately following conjugation might have 

 resulted differently. 



Second That the presence of one of these forms in the stomach 

 of the ox in no wise necessitates the presence of other forms. The forms 

 bicaudatum, tricaudatum, and cattanei, however, have never been 

 found except in the presence of forma quadricaudatum. 



5. The genus Diplodinium has been revised, as a result, in part, 

 oMhe discoverv of the three above-named forms, with the result that 



