No. 647] SHORTER ARTICLES AND DISCUSSION 569 



been found, eyelessness in these individuals was clearly not in- 

 herited. The lack of inheritance in these Moma rectirostris 

 would have been anticipated if due regard had earlier been 

 given to a peculiar feature of the head of these eyeless indi- 

 viduals. This will be discussed in a later paragraph. 



The next occurrence of eyeless Cladocera was in February, 

 1922, when seven eyeless Moina niacrocopa were found among 

 147 young of the third brood from 10 mothers in a crowded 

 bottle. The culture water in this bottle seemed rather cloudy, 

 an appearance known frequently to be associated with unfavor- 

 able conditions which sometimes result in death to part (;t all of 

 the Cladocera in such a bottle.' In the present case in addition 

 to one eyeless male and 6 eyeless females among the 67 females 

 and 80 males in the bottle, there were other abnormals — 6 or 8 

 with abnormal eyes (pigment reduced or eye not completely 

 formed) and perhaps an equal number with abnormal antenna 

 (certain segments missing, aborted or fused with others) and 

 one male with an abnormal eye and an abnormal antennule. 

 Some of the eyeless individuals and some with abnormal eyes 

 had abnormal antennsB also. Others showed abnormality in only 

 one feature. Since these abnormals appeared in a crowded bottle 

 (10 mothers) it is impossible to know, but they probably did 

 not come from a single mother. Among the next brood of 

 young from the same mothers were a few with abnormal an- 

 tennas and slightly abnormal eyes. Subsequent young were 

 normal. 



Early attention to an interesting feature of the heads of these 

 eyeless individuals removed any temptation to anticipate in- 

 heritance of eyelessness in these cases ; and, as expected, all the 

 numerous young examined from these eyeless individuals (and 

 from the other abnormals as well) were normal. Since in these 

 cases eyelessness was not hereditary some developmental acci- 

 dent would seem probably responsible for its occurrence. In- 

 deed, it seems fairly evident, in view of the occnrn>ii<M^ of orlit'i- 



that these abnormalities were related to some niif;i\ nrahl,^ fa.-- 



