30 Mr. G. A. K. Marshall on Seasonal Dimorphism 



the formation of the embryos ; at the very outset a mass 

 of cells is seen to isolate itself at the periphery, in the shape 

 of a crescent, which gradually increases in size and becomes 

 separated off to form, in all probability, the granular mass 

 which fills the amniotic tube and encompasses the embryos. 



The result of the foregoing observation is therefore the 

 discovery of a mode of reproduction which is entirely new 

 among the Arthropoda, and of which it is difficult, I think, 

 to find an equivalent among the Metazoa. Now, how are 

 we to interpret this curious case of metagenesis? Must we 

 consider the tube containing the chain of embryos as a nurse, 

 of which the soma would be represented by the epithelial 

 tube and by the internal cells which do not participate in the 

 formation of the embryos ? We cannot help thinking of the 

 Cysticerci and the Orthonectida ; but comparisons of this 

 sort would at present be injudicious. We prefer to confine 

 ourselves to the facts, waiting for their general interpretation 

 until the observations which we are pursuing upon different 

 species furnish us with more ample data. 



VI. — Seasonal Dimorphism in Butterflies of the 

 Genus Precis, JUoubl. By Guy A. K. Marshall, F.Z.S. 



It is now nearly two years since I recorded my conviction 

 (Trans. Ent. Soc. 1896, p. 557) that seasonal dimorphism of a 

 singularly marked character existed among certain African 

 species of the genus Precis. This opinion, based as it was 

 on field observations alone and not on actual breeding experi- 

 ments, did not appear to receive general acceptance ; and this 

 is perhaps hardly to be wondered at seeing how very marked 

 are the differences between such forms as octavia and sesamus, 

 simia and cuama, archesia and pelasgis, &c. 



The only counter evidence of any importance, however, 

 which has come under my notice is that adduced by that 

 eminent entomologist Mr. W. L. Distant in his interesting notes 

 on Transvaal butterflies (Ann. & Mag. N. H. (7) vol. i. p. 51). 

 He there says, (i I found Precis octavia var. exceedingly scarce 

 in the Transvaal, having only secured one specimen at Pretoria. 

 1 have since received another example from Johannesburg. 

 P. sesamus, on the contrary, was very abundant, and always 

 during the wet or summer season, frequenting my small 

 flower-garden. Hence 1 have found no evidence for the pro- 

 position made by Mr. Guy A. K. Marshall that the two species 

 are identical, or, rather, that P . octavia is the wet-season and 



