of the Fishery Board for Scotland. 



195 



the head. Vet even this is a doubtful character ; for specimens may be 

 obtained in this loch both with and without the tooth which are other- 

 wise identical (figures 32, 33). Figure 29 represents a very common 

 form among the Loch Leven Daphnice; while figures 30 and 31 represent 

 specimens in which the posterior spine is almost or altogether obsolete. A 

 few males were observed in the gatherings from this loch collected in 

 December. 



The Daphnue of Duddingston Loch. (Plate VII., figures 41-44, 44a, 



46, 54.) 



Daphnia hyalina, var. pellucida, P. E. Miiller, is recorded by Dr. 

 Brady from Duddingston Loch, which appears to be the only loch in 

 Britain where this variety has been observed. As the distribution of this 

 form appears to be so restricted, the following description of the female, 

 transcribed from Dr. Brady's Revision already referred to, may be of 

 interest : — 



"Female. — Outline as seen from the side subovate, with a very long, 

 slender, and slightly curved spine. Head occupying about one-third of 

 the length of the body, well-rounded in front, ventral margin straight or 

 very slightly sinuated, and terminating in a slighily produced beak ; 

 dorsal border of the shell forming a continuous very gentle curve, some- 

 what flattened in the middle ; ventral margin rather boldly convex. The 

 post-abdominal spines are slender and simple, except for a fringe of 

 excessively delicate setse, progressively increasing in size from behind 

 backwards ; dorsal abdominal processes obsolete. Eye rather large, placed 

 near the centre of the head ; between it and the rostrum is generally 

 visible a minute eye-spot. Shell often very distinctly chequered; in other 

 cases nothing but a granulated structure is visible. Length, l*8mm. ; 

 height, '9mm." 



During the four occasions on which Duddingston Loch was examined 

 no satisfactory examples of the variety described above were observed. 

 The Daphniai that were collected showed a certain amount of variation in 

 the general outline, in the length of the posterior spine, in the number of 

 preanal teeth on the post-abdomen, and in the development of the post- 

 abdominal processes. Some of the more or less immature specimens 

 resembled somewhat the variety described by P. E. Miiller, but the most 

 common appearance assumed by the adult female is that represented by 

 figure 41. The post-abdomen of this specimen is shown by figure 46. 

 The length of this specimen, exclusive of the posterior spine, is about 

 l'9mm. ; but it measures, including the spine, 2 •5mm. The head is a 

 very little more than a fourth of the total length of the body. The pre- 

 anal spines are ten, but in some specimens they amount to fourteen. The 

 abdominal processes are moderately developed, and the post-abdominal 

 claws are similar to those of D. lacustris or D. longispina. I have not, so 

 far, observed any of the young with a vertex tooth. Male specimens were 

 not very rare in the gathering collected in September last, and one of 

 them is represented by figure 43. Had the young been furnished with a 

 vertex tooth, I would have been inclined to ascribe the Duddingston Loch 

 Daphnia captured in our tow- nets to T). lacustris ; but as no young pos- 

 sessing such a tooth have been observed, the species with which they most 

 closely agree is D. longispina. Figure 44 represents the head of a not 

 very mature specimen, and figure 44a its abdominal processes. 



The Loch Doon Daphniai. (Plate VII., figures 36, 39, 50.) 

 The Daphnue of this loch are of a somewhat peculiar form that appears 



