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PROCEEDINGS OF THE NATIONAL MUSEUM 



the total number, a striking contrast to the conditions in bisexual 

 populations. If we count the incomplete rings as counterparts of 

 whole rings we might say that the population is nomomeristic. But 

 I will not go so far as that. We cannot say for certain how the 

 incomplete rings are to be interpreted. In any case, this analysis 

 shows that we must consider these structures. If they had not been 

 counted here v/e would have obtained a vsTong impression of the 

 variation. 



In small lots, of course, we shall not infrequently find all specimens 

 to have the same number of rings. The largest lot in which I observed 

 this fact is from St. Paul Island, Pribilof Group, and contains 20 

 females, all having 27 body-rings. The number of specimens is, 

 however, too small to enable us to draw any conclusion. 



A few specimens of L. arcticus with 26 or 28 rings have been observed 

 by me, but only in samples with males. These, like the majority of 

 those without males, contain only very few specimens, as may be 

 seen from the following lot of 14 specimens of L. arcticus from Cam- 

 bridge Bay, Canada (U.S.N.M. No. 180638) : 



Of L. apus, I have had access only to samples with few specimens. 

 A representative example is the following lot of 17 females from Malma 

 at Uppsala, Sweden (Uppsala Museum) (no males were found in the 

 sample) : 



Here we probably have a parthenogenetic population, because males 

 of this species have never been found in Sweden. The range of varia- 

 tion is greater than in the sample of L. arcticus from Alaska, but it is 

 interesting to notice the predominant representation of specimens 



