ANATOMY OF ARACHNIDS 11 



As Koenenia is exceedingly minute, its organs and the cells 

 composing them are all on a correspondingly minute scale, so 

 that it is not by any means easy to make out the different parts 

 of the gland, and it is only by studying a large number of speci- 

 mens that one can come to satisfactory conclusions. There is a 

 small circular saccule in segment II consisting of eight or ten 

 fairly well defined cells enclosing a lumen, from which a short 

 collecting duct of five of six cells leads into a long narrow sac 

 which extends posteriorly into the abdomen to segment VIII 

 (genital), where it forms a short loop and ends bhndly. As al- 

 ready observed by Borner, the cells of this posterior loop differ 

 from those of the straight part of tlie sac, and he quite rightly 

 remarks that none of the cells, either in the loop or in the straight 

 part of the sac, have a striated base; i.e., they are secreting, not 

 excreting cells such as one finds in the true labyrinth of the 

 arachnids. Just below the point at which the collecting tubule 

 or duct changes to the long sac, there is an opening leading into 

 a dilated vesicle, and from the vesicle there is a short exit tubule 

 leading to the outlet just posterior to appendage II (diagram 3, 

 fig. 2). 



It seems obvious that this organ must be homologous with 

 the coxal gland of the Sohfugae rather than with that of the 

 scorpions and spiders. The saccule and outlet are on the same 

 segment (II), and we also find the same long sac with a coil at 

 its posterior extremity extending far back and lined with secret- 

 ing cells. In Koenenia, however, the true labyrinth has prac- 

 tically disappeared as such, being represented merely by the 

 vesicle, which probably only acts as a reservoir for the products 

 of secretion, having no excretory functions, since the walls of 

 the vesicle do not appear to be lined with striated epithelium. 

 - It may be further remarked that if this long sac represented 

 the true labyrinth, not only should it be lined with striated cells 

 but it would necessarily have to loop forward on itself and run 

 forward again to the outlet, thus forming a double tubule on 

 cross section at any point ; but it is a single tube throughout and 

 has been correctly so described by both Grassi and Borner. 



