374 Proceedings of the Royal Physical Society. 
also in those made in Loch Tay. The Rev. A. M. Norman 
obtained it in Lochmaben Loch, Dumfriesshire. When alive, 
its presence in the water can only be detected by the black 
pigment-spot that constitutes the creature’s eye. Leptodora is 
a large Cladoceran ; some of my specimens from Loch Leven 
measure at least three-eighths of an inch in length, but with 
the exception of the black eye-spot it is perfectly transparent; 
hence, though by no means rare in Britain, it had been 
overlooked even by such a careful observer as Dr Baird, and 
was only discovered when the Rev. A. M. Norman examined 
Lochmaben Loch, a locality that had previously been ex- 
amined by Dr Baird. 
With Leptodora hyalina I completemy list of the fresh-water 
Cladocera observed within the district around Edinburgh; 
and this also finishes, for the present, my enumeration 
of the land and fresh-water Crustacea of the area. 
In my first paper I recorded one Amphipod and nine 
Isopods, and in the second paper thirty-five Ostracods and 
twenty-one Copepods, for the district; in the present paper 
I have recorded twenty-nine species of Cladocera, making 
the total number of species of land and fresh-water Crustacea 
recorded for the district around Edinburgh ninety-five. This 
number is likely to be considerably augmented when the 
district comes to be more thoroughly investigated. 
It may be of interest to those not familiar with the 
Entomostraca, if, before leaving this part of my subject, I 
should indicate one marked and characteristic difference in 
the manner in which the reproduction of the species is 
accomplished in each of the three large groups of the 
Entomostraca dealt with in the preceding lists, viz., the 
Ostracoda, the Copepoda, and the Cladocera. 
The Ostracoda may be described as the “ oviparous group.” 
In this group the eggs are usually deposited on floating or 
submerged leaves of aquatic plants, pieces of wood, ete., or 
on stones at the bottom, and are left there-to hatch out, 
without apparently any further parental care. 
The Copepoda and Cladocera, on the other hand, may be 
described as the “ ovoviviparous groups,” but with this differ- 
ence between them. In the Copepoda the eggs are usually 
