C. DOBBLL 161 



81. Teratological variations' are not very uncommon in ciliates, 

 especially in old cultures. One naturally wants to know the genetic 

 behaviour of monstrous characters, and fortunately some information 

 has already been elicited. Balbiani (1893, p. 56, PI. II, figs. 44, A— N) 

 was, I think, the first to describe the inheritance of an abnormality. 

 He cut a Paramecium, aurelia transversely, and the posterior individual 

 of the two so formed regenerated and later divided. " In the course of 

 the fourth generation an abnormal prolongation in the form of a horn 

 developed on the anterior individual." It persisted during seven 

 subsequent generations, passing to the anterior daughter-individual 

 at each fission, but gradually moving further backwards. Finally it 

 passed to the posterior end of its last possessor, which then died. The 

 sister-organisms appear to have been normal and " hornless " in every 

 case. 



82. A comparable case was recorded by Simpson (1901). Of four 

 descendants of a normal exconjugant Paramecium caudatwiu three were 

 normal, but the fourth " developed a cleft tail." This animal continued 

 to divide for several generations. The abnormality persisted in the 

 posterior individual at each division, becoming gradually modified from 

 a "cleft tail" into a long "dorsal lobe." After eight divisions, the 

 abnomial animal died. In every case the anterior sister-individuals 

 were normal. 



83. More extensive investigations of the inheritance of such 

 abnormalities have been undertaken by Jennings (1908). He isolated 

 abnormal Paramecia" (with "horns" or "spines," truncated ends, etc.) 

 and studied the fate of the peculiar features during subsequent fissions. 

 In many cases the abnormality gradually disappeared — the normal form 

 being gradually regained in a few generations. Sometimes, however, 

 the animals or their descendants became still more monstrous, and 

 finally died. No permanently abnormal races were ever obtained by 

 selecting monstrous individuals. 



' Attention was first called, I believe, to ciliate monsters by Tatem (1870) wbo described 

 two specimens of Chilodon and one of Trachelius in which th'e "lip" was abnormally pro- 

 longed. His comment is worth quoting : "Malformations such as those I have cited have, 

 in my opinion, avalue beyond that of mere curiosities. ..for may theynot help to determine 

 the fixity or otherwise of a species through aberrant forms ? and thus a better knowledge 

 of what is to be regarded as essentially specific be ultimately arrived at." Curiously 

 enough, another "monster" described by Tatem is now recognised as a distinct ppecies 

 (Vorticella monllata). 



'' The species studied "had the characteristics usually attributed to Paramecium 

 caudatum. " 



