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Part III. — Seventeenth A n imal Report 



Diaptomus hircus, Brady, var. — A Diaptomus, frequent in Loch Ness, 

 Loch Oich, and Loch Lochy, which appears to represent one of several forms 

 which agree in having a more or less close relationship with Diaptomus 

 salinus, Daday. There is a certain uniformity of structure in the fifth 

 thoracic feet of the males of this group which indicates their relationship, 

 but there is also a certain diversity between the different forms composing 

 it, which, if it were constant, might constitute a satisfactory basis for 

 the separation of the various forms and for distinguishing the one from the 

 other. It appears, however, that this diversity is not constant. Speci- 

 mens are met with in which the characters of different forms seem to 

 blend ; so that it is sometimes difficult to decide as to the species to which 

 thev should be ascribed. It also lends support to the opinion that after 

 all. these various forms, as in the case of certain Daphniw to be referred to 

 later on, may be but modifications of one variable type. For the present 

 I am inclined to ascribe the Diaptomi from the three lochs mentioned to 

 Diaptomus hircus, Brady, as being the species to which they are most 

 closely related, though differing in one or two points. For example, the 

 appendage at the end of the third-last joint of the right male antennule 

 is not fimbriated ; the protopodite of the left foot of the fifth pair in the 

 male wants the finger-like hyaline appendage on the inner margin ; and 

 the last joint of the outer branches of the same pair of feet in the female 

 is furnished with two sub-equal setae : these characters appear, however, 

 to be more or less variable. A somewhat similar form of Diaptomus 

 was obtained sparingly in Loch Katrine. Figure 5 on Plate XIII. repre- 

 sents one of the Loch Oich specimens. It measured fully one and a half 

 millimetres in length. Figures 6 and 7 represent one of the fifth pair of 

 feet of the female and the male fifth pair ; and figure 8 shows the last 

 three joints of the male right antennule. 



Diaptomus wierzejskii, Richard. — One or two specimens, apparently 

 belonging to this form, were obtained in Loch Achray, but the species 

 appears to be very rare. One of the more obvious characters of this 

 Diaptomus is the moderately large and serrated appendage at the end of 

 the third-last joint of the right antennule of the male. D. wierzejskii is 

 considered to be identical with D. serricornis, Lilljeborg, but there seems 

 to be some difference of opinion as to which of the two names should take 

 precedence. Professor G. S. Brady has given the preference to Lilljeborg's 

 name,* but Dr. 0. Schmeil t has shown that though the two names were 

 published within a very short time of one another, Richard's was really 

 the first in the field. Both names were published in the same year and 

 in the same volume, Richard's at page 53 and Lilljeborg's at page 157. 

 D. wierzejskii is one of the Diaptomus salinus group. 



The Harpacticid^e. — Among the Harpacticidse observed in the different 

 lochs there are a few that may be specially referred to here : — 



Oanthocamptus minutus, Claus, though only recorded within recent 

 years as a member of the British fresh-water fauna, is apparently a 

 widely-distributed species in Britain. It was observed in each of the 

 eight lochs composing the first series of those now under discussion. 



Cantliocamptus inornatus, a species described in one of the recent 

 reports of the Fishery Board, has had its distribution still further extended 

 by these researches. It was observed in four of the present series of lochs. 



Oanthocamptus schmeilii, Mrazek. — This interesting species, which was 

 observed for the first time in Britain in Loch Leven, and some time 



* Revision of the British Fresh-water Cyclopidte and Calanidte, p. 36 (1591). 

 + Deutichlauds freilebende Siisswasser — Copepoden, Part ITT., p. 55 (1896). 



