242 D. J. SCOURFIELD ON EPHIPPIA OF LYNCEID ENTOMOSTRACA. 



female of Chydorus sphaericus as early as February, but there is 

 no doubt that the two periods mentioned are the best times to 

 search for these productions. 



Before concluding this account of the Lynceid ephippia, I would 

 like to draw attention to the fact that a detailed study of these 

 bodies is not only interesting from a morphological point of view, 

 but will, without doubt, turn out to be very valuable to the 

 systematist. It must have been observed during the course of 

 this paper, that in many cases the different genera are character- 

 ised by well-marked types of ephippia, and that even species of 

 the same genus may vary very considerably in this respect. The 

 most striking case, perhaps, is tliat of the genus Alona, in which, 

 out of four species described, we have at least three distinct types 

 of ephippia. In Alona temiicaudis the wdiole shell is used, and 

 the egg is embedded in " packing " ; 'u\ A. costata (and perhaps 

 also in A. affinis) the anterior ventral portions of the valves 

 are detached, and the egg is surrounded by simple membranes ; 

 and in A. rectangula the whole ventral third of the valves is 

 thrown off, and the egg is enclosed in a delicate cellular tissue. 

 Other instances of these marked dififerences within a single genus 

 are to be found in Camjytocercics, Aloneila, and Chydorics. In 

 fact, the more closely the ephippia are studied, the more clearly it 

 is seen that we have in them valuable auxiliary specific characters. 

 But it cannot be too strongly insisted upon that it is, as a rule, 

 only in the moulted ephippium that all the peculiarities, especially 

 the course taken by the line of weakness and the character of the 

 inner membranes, can be properly made out. It is not enough to 

 describe the ephippial females. This should, of course, be done 

 wheie possible, but it would be rendering still greater service to 

 the study of the Cladocera if the thrown-off ephippia could also 

 be described wherever possible. 



It now only remains for me to express my warmest thanks to 

 Professor G. 0. Sars for his great kindness in sending me so many 

 important examples of ephippia and ephippial females. I only 

 hope that I have dealt with the material so generously placed at 

 my disposal in a way which will at least be found to throw a little 

 fresh light on the subject, and have the effect of stimulating 

 others to take up and continue the work. 



