i897-9 8 -] The Upper Elf Loch, Braids. 379 



In some of the Daphniadre, and perhaps also in some of the 

 other groups, broods of these pseudova are produced at more 

 or less frequent intervals, and sometimes in considerable 

 numbers during the life of the female ; but in most of the 

 Lynceidre the production of summer eggs does not appear to 

 be so frequent or so numerous. The winter- or resting-eggs 

 — the latter name, as will be apparent from what follows, is 

 the more appropriate one — are said to be true fertilised eggs, 

 and they are produced usually towards the close of the life 

 of the female, their production being her last efforts for the 

 propagation of the species. In the Daphniadte, and probably 

 also in the Lynceidee, — certainly in some of them, — these 

 resting-eggs are enclosed in a portion of the test of the 

 mother that is somewhat modified for the purpose, and is 

 technically called the ephippium (Gr. ephippion, a saddle, from 

 its shape). Speaking generally, two resting-eggs are produced 

 in the Daphniadie, but only one in the Lynceidae. These 

 eggs appear as dark-coloured, or almost black, oval bodies, 

 within the ephippium. The production of the ephippia is not 

 limited to autumn or winter, as they may be produced at any 

 season, just as the so-called summer eggs may be observed at 

 all seasons — in winter as well as in summer. Eesting-eggs, 

 after being set free, and whether enclosed in a true ephippium 

 or not, may, and frequently do, lie dormant for a considerable 

 period, hence the name " resting-eggs." It is doubtful if the 

 causes that in due time excite the active development of these 

 resting-eggs are yet clearly understood : increase of temperature 

 may have something to do with it. Ephippia enclosing one or 

 two eggs are often met with by the pond-worker, and occa- 

 sionally prove a source of perplexity : it is therefore hoped 

 that what has just been stated as to their true character may 

 prove useful to some. 



Another interesting feature in the history of the Cladocera 

 is the entire absence, or extreme rarity except at irregular 

 and more or less distant intervals of time, of the males of 

 many of the species. The Daphniada? may be referred to 

 as furnishing examples of this phenomenon. The female 

 Daphnia is frequently very prolific. She may develop brood 

 after brood of young at short intervals for a considerable 

 time, and these young, in their turn, may give birth to other 



