ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 41 3 



there is marked sex dimorphism, but the males are very polymorphic, 

 and some have come to be very like females. The female characters 

 may be assumed on the head (gynsecocephaloxs), afterwards on the 

 thorax (hemigynous), aud finally on the elytra (homceomorphic). There 

 is in the males in successive stages a variation towards characteristics 

 of the female, " periodic poecilaiidry " in short. 



Ocelli.* — Dr. O. E. Imhof gives a summary account of the number, 

 size, and arrangement of the ocelli in Diptera, and proposes to do the 

 same for all insects. The precise object in view is not explained. In 

 his introductory notes he observes that 3 is the commonest number ; 

 the occurrence of 6-12 is rare ; only in Collembola is the presence of 

 more than 3 (up to 18) of general occurrence. The predominant 

 arrangement is a frontal triangle, but there are occasionally lateral 

 groups, and very rarely the ocelli are on the under side of the head. 



Phagocytosis in Postembryonic Development of Diptera.f — Prof. Y. 

 L. Kellogg contrasts the larva of Holorusia rubiginosa — a giant Tipulid 

 whose immature stages are now for the first time described — and the 

 larva of Blepharocera capitata. 



In the latter there is a great breaking down of the larval organs ; the 

 musculature, the alimentary caual, and the respiratory system are largely 

 broken down and re-formed ; and in all of this histolysis (18 days) 

 phagocytes are abundant and conspicuous. In Holorusia, however, 

 with its 12 days of pupal condition, histolysis is unaccompanied by 

 phagocytosis. The condition in which the histolytic phenomena occupy 

 the longer time is the one in which the histolysis is accompanied by 

 plagocytosis. 



Prof. Kellogg suggests that the explanation may be as follows : — In 

 Blepharocera, with its highly specialised larval form, its peculiar and 

 specially developed organs, the change to imago is radical ; the histolysis 

 of larval tissues is extensive. In Holorusia, with its generalised larval 

 form and its less modified organs, the change to imago is accomplished 

 with much less breaking down of larval organs and re-formation of ima- 

 ginal ones ; the histolysis is less radical and considerable. The phago- 

 cytes are the agents or the assisting agents in the more extended aud 

 radical histolysis. 



Cephalic Glands of Collembola.J — Victor Villeni has studied these 

 structures in Sminthurus and Orchesella, and has reached conclusions 

 differing from those of Folsom § on Orchesella, especially as regards the 

 course of the salivary duct, the structure of the labium, and some other 

 points. He is of opinion that Sminthurus is eminently well adapted for 

 the study of these structures, and that certain primitive characters 

 possessed by it shed light upon the condition of parts in Orchesella, 

 which is more difficult to study, and whose more specialised nature has, 

 as he believes, led Folsom astray. 



Formation of Eggs in Apterygota.|| — A. Lecaillon has made out 

 some interesting points in this connection. He finds that four different 



* Biol. Ceutralbl., xxi. (1901) pp. 189-92. 



t Anier. Nat., xxxv. (1901) pp. 363-8 (2 figs.). 



t Arch. Biol., xvii. (1900, published 1901) pp. 653-71 (2 pis. and 4 figs.). 



§ Cf. this Journal, 1899, p. 595. 



|| Comptes Kendus, exxxii. (1901) pp. 5S6-8. 



