602 BlilTISH ORIBATID^. 



From the above facts I think that we may fairly 

 conclude that in the Orihatidm coition probably takes 

 place by a bursa copularix within the anal plates and 

 in immediate proximity to the anus, and not at the 

 vulva of parturition within the genital plates. 



The Heart in Acarina. 



In vol. i, at p. 181, 1 drew attention to Dr. Kramer's 

 observation on the heart in GamaMis, as being, I believed, 

 the only instance where any acarologist or anatomist 

 had published any account of the existence of such an 

 organ in the Acarina. Since vol. i was issued, this organ 

 has been re-discovered by Herr Willibald Winkler. Prof. 

 Clans and Herr Winkler, not knowing of Kramer's 

 paper, stated the discovery as being new, and it naturally 

 attracted considerable attention ;* subsequently, how- 

 ever, they fully acknowledged Dr. Kramer's priority. f 

 Winkler succeeded in making more exact observations 

 than Kramer had done ; he describes the heart as very 

 delicate, composed of a single chamber, and as having 

 two paired ostia on the dorsal side and an aorta 

 running straight forward in the median line and ter- 

 minating with an open end above the brain. Winkler 

 discovered a similar organ in Ixodes ; and, in the first 

 notice, it was suggested that it might probably be found 

 in all Acarina. I have not, however, heard that anyone 

 has, up to the present time, succeeded in finding it in 

 any other family. Since the appearance of Winkler's 

 paper, and with the assistance that it affords, I have 

 carefully searched for the organ in living specimens of 

 young larvae and nymphs of Orihatidce, and in adults 

 which had just emerged and were still transparent. 

 This was Winkler's mode of observation, he was not 

 able to find the organ in dissections or sections. My 



* " Ueber das von Willib. Winkler aufgefundene Herz der Gama- 

 siden," ' Anz. Ak. d. Wiss. Wien,' Dec, 1885, pp. 250—253. 



t " Das Herz der Acariden," ' Arbeit, d. Zool. Inst, zu Wien,' Baud 

 vii, Heft 1. 



