344 PROFESSOR E. RAY LANKESTER, 
whom it is necessary to cite who have dealt with the struc- 
ture of Apus are: Grube (*‘ Bemerkungen iiber die Phyllo- 
poden’’), in the ‘Archiv f. Naturg., 1853; Baird, in his 
‘ British Entomostraca,’ Ray Soc., 1850; Claus, in a paper 
published in the ‘Gottingen Abhandlungen,’ vol. xvii, 
1873, entitled “Zur Kentniss des Baues und der Entwick- 
lung von Branchipus stagnalis und Apus cancriformis ;” 
Huxley, in his ‘ Anatomy of Invertebrate Animals,’ 1877, 
p- 281; Gerstaecker, in Bronn’s ‘ Classen und Ordnungen 
des Thierreichs,’ “ Crustacea,” p. 860, &c., plates xxx, xxxil, 
1879; and again, Claus, in the last edition (now in course 
of publication) of his ‘Handbuch der Zoologie,’ p. 527, 
1880. 
Having made a careful examination of the appendages 
of Apus cancriformis, of which I have received numerous 
specimens from the neighbourhood of Munich, from Prag, 
and from Padua, through the kindness of Professor von 
Siebold, of Professor Fricz, and of Professor Pavesi, respec- 
tively, as also of a specimen of Apus Dukii from Affghanistan, 
which I owe to the kindness of Surgeon-Major Day,’ I was 
surprised to find that neither Zaddach nor any one of the 
authors above cited gives a full account of these structures. 
Moreover, I found my results to be at variance on one or 
more important points with the statements of each of my 
predecessors, who also differ from one another as to the in- 
terpretation of some portions of the series of limbs. 
The most complete set of figures is that given by Professor 
Gerstaecker of the appendages of Apus productus, which are 
incorporated with reproductions of the figures of Zaddach, 
Claus, and Brauer,? in the plates of his valuable treatise 
on “ Crustacea’ (Bronn’s ‘ Thierreich’). 
These original drawings, and the interpretation put upon 
them in the explanation to the plate, appear to me to be so 
inaccurate that I think that my sketches, reproduced in the 
plate (Plate XX) accompanying this paper, and the following 
observations, may be found of value as a contribution 
towards a true history of the “‘ Krebsartige Kieferfuss” of 
Schaeffer. 
DeEscRIPTION OF THE APPENDAGES. 
The modified limbs or lateral appendages of Apus may be 
divided into four series, according to their position, viz.—l. 
1 This form, recently described by Mr. Day, is perhaps the 4. Himalayanus 
cited in Gerstaecker’s list. 
3 *Sitzungsber. der Akad.,’ Wien, Bd. lxix. 
