Dr. A. Krohn on the Male Generative Organs o/Phalangium. 151 



In support of this view I may refer to the data already extant 

 as to the development of the semen in some Arachnida (see 

 Von Siebold, Vergl. Anatomie, p. 544, note 6; and Leydig, 

 " Ueber den feineren Bau der Arthropoden," in M tiller's Archiv, 

 1855, p. 470). 



Mature semen is usually found in greater or less abundance 

 in the entire portion of the vas deferens before the dilatation. 

 The seminal corpuscles are rounded structures, furnished, I 

 believe, with a disciform nucleus. The oscillating movement 

 which is observed in them when they are not too closely pressed 

 together appears to be referable to the phenomenon of the so- 

 called molecular movement*. 



The two accessory glands situated in the anterior portion of 

 the abdomen immediately above the sheath of the penis are con- 

 nected by connective tissue and tracheal ramifications with the 

 coil of the vas deferens, which is placed between them. Their 

 intimate structure is founded on the same plan that has been 

 made known to us in the glands of many insects by the ad- 

 mirable works of H. Meckel, and especially of Leydig. Thus 

 we may distinguish in them a homogeneous external envelope 

 (tunica propria), a subjacent, proportionally thick layer of se- 

 creting cells, and within this a lining membrane (intima). The 

 lumen of the lobules or cseca appears to be a comparatively 

 narrow canal, from the circumference of which, throughout the 

 whole length of the canal, numerous fine tubules pass deeply 

 into the cellular layer. In the male of P. opilio (P. cornutum) 

 single tubules are seen at intervals, which are distinguished 

 from the rest both by their greater size and by their branching 

 within the cellular layer. The canals of all the sacs, after 

 uniting to form larger branches, finally combine into a main 

 duct extending forward through the midst of the gland, and 

 opening upon the upper wall of the sheath of the penis not far 

 from the sexual aperture. This duct, however, is never free, as 

 the layer of secretion-cells is continued upon it and envelopes 

 it as far as its outlet. The orifices of the two main ducts at the 

 point just mentioned lie close together on each side of the 

 median line. On the lining membrane of the main ducts and 

 their first branches a so-called spiral filament, similar to that 

 of the tracheae, may be detected. In the male of P. opilio it may 

 be pretty clearly distinguished even on the above-mentioned fine 

 tubules which penetrate the cellular layer. 



* I have not been able to give a satisfactory description of the appear- 

 ance of the seminal corpuscles under a high magnifying power. Accord- 

 ing to Leydig's investigations, they are round, flat structures, with a cen- 

 tral band-like elevation. Leydig regards their oscillating movement as 

 quite spontaneous, and therefore assumes that they probably possess a fine 

 capillary appendage {I.e. p. 469, pi. 17- fig- 41 d). 



