THE AMERICAN NATURALIST. [Vol. XXXVII. 



organs is greater than that existing between the two symmet- 

 rical groups of one segment. That is. the morphological kinship 

 between successive segments is greater than the likeness between 

 the two sides of a segment. 



In trying to trace the ancestral history of any species, resem- 

 blances which point toward a related species are valuable. We 

 have these in Lithobius forficatus and L. multidentatus. The 

 drawings of the two types of coxal pores, Figures 9 and 10, 

 show how the normal condition in L. forficatus can be suggested 

 by variations in L. multidentatus and vice versa. We know that 

 the first condition of the pores in both species is the same, a 

 single row of small round pores. This is probably the ancestral 

 condition. A fusion of two pore rudiments in L. multidentatus 

 would give the oblong shape natural in L. forficatus and to be 

 seen twice in the drawing of L. multidentatus. On the other 



pores of L. forficatus (left hand upper coxa) would result in a 

 two rowed condition. How the many rowed condition arises 



coxal pore patterns in general is a subject for further study. 

 That abnormalities in one species may indicate the normal con- 

 dition in a related species has been shown by Davenport (00). 



Summary. 



1. A place-mode is furnished for Lithobius forficatus, for the 

 years 1899 and 1900, at Cold Spring Harbor, Long Island. 



2. Length of body has essentially nothing to do with the 

 number of antennal joints in specimens 15 mm. long or more. 



3. Length has very little to do with the number of proster- 

 nal teeth. 



4. Length has some hearing on the number of coxal pores 

 in the adult, the correlation being closer on the 13th and 14th 

 legs than on the 12th or 1 5th legs. 



5. Coxal pores show a greater segmental or serial correlation 

 in the case of the 13th and 14th legs than bilateral symmetry. 



6. Variations in the one species of Lithobius point toward 

 the normal condition in the other species under consideration. 



