APPENDIX I 



On comparing the East Spitzbergen species found by 

 Professor Kiikenthal with the West Spitzbergen species 

 found by Professor Nathorst, we concluded that they are 

 identical, but that L. Spitzbergensis differs considerably 

 from L. glacialis in size and in the shape of the caudal 

 plate. We were at first disposed to consider it a new 

 species, especially on account of its possessing second 

 antennae which were said to be wanting in Lepidurus 

 glacialis. Closer examination, however, showed it to be a 

 small variety of L. glacialis, most probably derived from 

 the latter by being obliged to ripen at an earlier stage of 

 development, in adaptation to the shortness of the more 

 northerly summer. 



That this view is correct seems probable from the fol- 

 lowing considerations : 



(i) The possession of second antennae does not dis- 

 tinguish it from L. glacialis, for we have succeeded in 

 finding these appendages on the latter. 



(2) The position of the sperm-forming centre (see § on 

 reproduction) is identical in the two. 



(3) The genital tube is very much simpler, the diverticula 

 showing hardly any traces of branching, therein exhibiting 

 a more larval condition. 



(4) The same may be said of the smaller size of the 

 caudal plate, which develops gradually, as Brauer has shown 

 in his paper on the development of L. productus. 



U 2 



