19o1-1902.] The Entomostraca of Mid-Lothian. 305 
VIlL—NOTES ON THE ENTOMOSTRACA OF 
MID-LOTHIAN. 
By Dr T. B. SPRAGUE anp Miss B. SPRAGUE. 
(Read Feb. 26, 1902.) 
_ OvR principal object in this paper is to give the Society some 
account of the work done in connection with the recent com- 
petition for the prize offered by the Society for the best col- 
lection of freshwater crustacea from Mid-Lothian ; and we are 
not without hope that we may thus induce other members to 
take up the same interesting study. We shall touch briefly 
Bon the three divisions of the entomostraca, noting some of 
their habits and characteristics ; and shall then explain our 
7 of collecting and preserving; and finally, describe 
Some of the localities visited, and some of the more striking 
species obtained. Only two out of the sixty species we found 
are large enough to be examined without the help of a 
Microscope. These two are the Asellus aquaticus or “ water 
_ woodlouse”, a creature resembling the common woodlouse or 
3 “slater”, to which it is nearly related; and the Gammarus 
_ pulex or “freshwater shrimp”, which is almost identical in 
appearance with the familiar sandhopper. The remaining 
ji 58 species are all included under the general term “ ento- 
_mostraca”, and fall into three divisions,—the Copepoda, Ostra- 
coda, and Cladocera. It may be worth while to note what 
these names mean: “Copepoda” means literally “oar-feet ”, 
and refers to the fact that all the species in this division use 
their feet in swimming. “Ostracoda” means “ having the form 
of a shell”; all the ostracods resemble more or less closely 
tiny bivalve shells; when the creature is at rest, the whole 
of the limbs—antennas and legs—can be tucked inside the 
Shell, leaving nothing exposed. “Cladocera” means “ branch- 
horned,” and denotes those entomostraca which have a two- 
_ branched antenna instead of a simple one. 
__ Taking the copepods first, we find that they are all more or 
“less shrimplike in appearance, the body being composed of a 
“number of segments protected by as many distinct rings of 
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