JOURNAL 
OF THE 
ROYAL MICROSCOPICAL SOCIETY. 
SEPTEMBER, 1922. 
TRANSACTIONS OF THE SOCIETY . 
VIII.— THE GAMETO GENESIS OF NEPA GINEREA 
(WATER SCORPION). 
By E. A. Spaul, B.Sc., F.Z.S., Department of Zoology, 
Birkbeck College, University of London. 
(Bead June 21, 1922.) 
Two Plates. 
A large amount of work has been done on the group Hemiptera 
(Wilson, Montgomery, Stevens and others), mainly on account 
of the ease with which its members can be obtained, and the 
suitability of the material when prepared for favourable study of 
cytological phenomena ; but so far, except for a brief reference, no 
observations have been made on the family Nepidse (Water 
Scorpions) belonging to the aquatic Rhynchota. It includes two 
common forms, Nepa and Ranatra, although the latter is now 
becoming rare and confined to the South of England. The work 
done so far consists of a few observations of Chickering on the 
spermatogonia of Ranatra , but although literature is scarce so far 
as this family is concerned, several papers on the closely related 
family Notonectidse have- been published by Browne, who has 
made detailed investigations. 
The water scorpions are rather sluggish in their movements, 
feeding on small insects and aquatic animals, and creeping 
leisurely about the bottom of ponds during spring and summer. 
The whole history of the germ cells of Nepa cinerea is found in 
the sex organs from spring up to midsummer, so that specimens 
captured in spring contain only spermatogonial divisions and 
early meiotic prophases, but those captured in the middle of the 
summer give spermatocyte divisions in addition. 
In the female there are two ovaries consisting of a number of 
ovarioles of the typical Hemipteran type, with the single large 
nutritive chamber at the apex connected by ducts with the 
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