2 ARKIV rÖR ZOOLOGI. BAI^ID 7. N:o 28. 



summer, during my researches on the acarofauna of the 

 neiglibourhood of Stockholm, I captured a fairly good number 

 of Sejus togatus C. L. Koch, nymphae and both sexes. The 

 examination of this species revealed some extraordinary fea- 

 tures which, in my opinion, throw some light on some 

 questions of a phylogenetical nature. 



Very likely not all my theories will meet with the ap- 

 proval of other acaridologists, but in that event my contri- 

 bution will presumably bring about a discussion on these 

 questions, which will turn the attention to them; and this 

 cannot but benefit the study of the comparative morphology 

 and the phylogeny of this group, a field which has hitherto 

 been much neglected, but for the study of which Reuter's 

 ingenious work on the morphology and ontogeny of the acari 

 has laid a firm foundation. 



On the dorsal shields. 



It is well known that in many genera there are two 

 dorsal shields; an anterior and a posterior one, separated 



Fig. 1, 



Fig. 2. 



Fig. 1. Heterogaiimsus claviger Tgdh. ef, dorsal view X 75 (af ter Trägård h). 

 Fig. 2. Eugamasus (?) ferox Tgdh. 9 » dorsal view X 20 (after Trägårdh). 



