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Part III. — Seventeenth Annual Report 



to be identical with Daphnia longispina, var. ?iasuta, G. 0. Sars. Loch 

 Doon appears to be the only British loch in which this variety has been 

 observed. It is the only Daphnia that I have noticed in the Loch Doon 

 gatherings, aud in one or two of them it was moderately common. A 

 slight variation is observable in some of the specimens, especially in the 

 contour of the head, but otherwise the form is a very constant one. 

 Figure 36 represents one of the more common forms. The head, seen 

 from the side, is narrowed anteriorly, and the ventral margin is slightly 

 convex, but more distinctly so immediately anterior to the beak. The 

 dorsal margin is boldly curved anteriorly ; it then extends in a nearly- 

 straight line to a little beyond the middle of the body, and thence curves 

 gently to the base of the posterior spine. The ventral margin from the 

 beak to the base of the posterior spine is prominently arcuate. The head 

 is equal to about a fourth part of the entire length of the body. The 

 posterior spine is of moderate length, but the length varies somewhat in 

 different specimens. The specimen represented by figure 37 is somewhat 

 larger than the one just referred to, and has the front and dorsal margins 

 of the head slightly concave. A male specimen which has the head more 

 evenly rounded, and possesses a longer posterior spine, is represented by 

 figure 38. The preanal spines of the post-abdomen figured (fig. 50), which is 

 that of a female, number thirteen; but the number varies to a small 

 extent in different specimens. The terminal claws are slender and of 

 moderate length; and the abdominal processes, which in the specimen 

 figured (fig. 50) are moderately developed, have also a slight tendency 

 to variation. Figure 39 shows a front view of a male specimen. 



The Daphnice of Loch Ness, Loch Oich, and Loch Lochy. 

 (Plate VII., figures 1-21, 47, 48, 52.) 



The Daphnice observed in these three lochs, though exceedingly variable 

 in form, appear all to be referable to the one species — D. galeata. Figure 

 1, which represents one of the largest and finest of the forms observed in 

 Loch Oich, measured about 3"4mm. (fully Jth of an inch) in length. 

 This is a common form in Loch Oich, but there are quite a number of 

 variations. Figures 2 and 3 represent two of these variations in which 

 the crest, though pointing forward as in figure 1, is scarcely so much pro- 

 duced ; while in figure 3 the beak is more produced than it is in figures 

 1 and 2. In figures 5 to 8, which represent other variations, the crest 

 assumes a more or less upright position. In figure 6 the head has the 

 form of an equilateral triangle. In figure 4, on the other hand, the beak 

 is somewhat prominent, but the head has lost its pointed form and becomes 

 somewhat rounded. Figures 18 to 20 represent another set of variations 

 in which, though the head be somewhat similar to that shown by figures 

 1 to 3, the posterior spine is either very short or obsolete. All the figures 

 just referred to were prepared from Loch Oich specimens and represent 

 adult females, i.e., females with pseudova or embryos, or in which an 

 ephippium was in process of development. Figure 17 represents a Loch 

 Oich male. Many of these w r ere examined ; but while variation among 

 the females was almost unlimited, there was very little variety of form 

 observed among the males ; and in no case was a male specimen observed 

 with a rounded head. Every one of the specimeus noticed was furnished 

 with a pointed crest; even the immature specimens possessed it. Where 

 any difference was observed among these male specimens, it was limited 

 very much to the prominence in front of the eye being more arcuate in 

 some than in others. 



In figures 11 to 16 a somewhat different group of variations is repre- 



