OF CHLOEON (EPHEMERA) DIMIDIATUM. 
491 
dimorphism of the mature form which we find, for instance, in ants and bees; it would 
therefore be convenient to distinguish it by a different name; and I have ventured to 
suggest the terms Dieidism and Polyeidism. 
The same considerations explain the remarkable fact that in alternation of generations 
the reproduction is agamic in the one form. This is because impregnation requires the 
perfection both of external and internal organs ; and if the phenomenon arises, as has 
just been suggested, from the fact that the internal organs arrive at maturity before the 
external ones, impregnation cannot take place, and reproduction will only result in those 
species which have the power of agamic multiplication. 
Time of moulting. State. No. of days. Time of moulting. | State, No, of nd 
| 
Specimen No. 1. Specimen No. 2 
Captured Sept. 8 4th Captured Ang. 17 9th 
Moulted  ,, 9 5th Moulted 2] 10th 
5 acd 6th 9 a ee SB llth 2 
» 33 15 7th 4 ” ” 30 J 2th 7 
» 33 18 8th 3 3 Sept. 6 13th 7 
» » 21 9th 9 4 a 4 14th 1 
p ae 10th 3 21898 ele Fe 10h : 
LE] ” 2 7 1 i th 3 » 21 pM | 
á 30 2th 3 ann] 108 6 | 
During October I was for|some days away from home. » Oct 4 d. 4 
su Oct. » » As 2 24 | 
ER) Nor. 2 m 9 55 Nov 6 17th 19 | 
» 33 I 7 l4th 1 5 » » os - 16 | 
» Dec. 8 = 21 ” Dec. 1 0 "» 19 | 
Nu M 15th 16 os ium | 
Lh Ju 7 14 Rudiments of | 
3 23 se 1 6 wi regii 1 9 | 
» Feb. 8 I 6th 16 ” Jan 18 abdominal seg- | 
” 3 FA 10 ment. | 
» March 1 17th 11 VAR 
2 » 10 M m " Feb : s 18 | 
So : à 33 20 , » Ma 1 2 
3 arch 6 ” 
| Rudiments of Re : 19th 18 | 
wings coverin, , g | 
LE] » 30 h of the 1 0 ger wine | | 
1st abdomina : Mr. te sdb | 
| segment. zc Am s; domina s| 8 | 
» April 10 " E XH | 
Rudiments of permet dd of | 
wings covering " | 
2 $5 29 ? ch of th . 10 ofthe Seda 9 
3rd abdominal » m 
ent. 
» May 14 Proimago. 4 x 
eon re, Ben 
