298 Herr J. Waffiiev oti the 



to' 



coxal ") glands. Long tubular glands have recently been 

 described by Sturany (No. 64, pp. 16-17) in Trombidium; 

 the author did not observe either their opening upon the 

 surface of the body or their union with the alimentary canal, 

 and he regards them as homologous with the coxal glands. 

 Yet, judging from his figure (fig. 21), it might be supposed 

 that he himself commits the error with which he reproaches 

 certain other observers, only in the reverse sense, namely, 

 that he regards the Malpighian tubes as coxal glands. 



If with respect to their excretory organs the Phalangidje 

 form the extreme stage in one direction, the Acarina occupy 

 tlie corresponding position in the other. In this way the 

 ^Jalpighian tubes of the Arachnids in the majority of cases do 

 not correspond either in function with those of the rest of the 

 Tracheata. The role of the Malpighian tubes of Insects (and 

 Myriopods) is in the case of the Arachnids fulfilled to a con- 

 siderable degree by the coxal glands or the liver. 



From all that has been stated, it appears to me that the 

 following indisputable conclusion may be drawn : — the Mal- 

 pighian tubes of the Arachnids are not homologous with the 

 Malpighian tubes of the rest of the Tracheates ; they are 

 structures analogous to the so-called Malpighian tubes in 

 certain Amphipods. Should this conclusion be confirmed by 

 further observations, it would be an important and positive 

 argument in favour of the separation of the Arachnida from 

 the Antennata. 



As regards the wide diflfusion of the (Malpighian) excretory 

 tubes in the Arachnids, this is apparently due to the very 

 early occurrence of these organs in the representatives of the 

 Arachnids. While speaking of this I should like to mention 

 certain considerations which might possibly explain the 

 absence of the organs in question in LimuluSy which in all 

 other respects so closely approaches the Arachnids. If we 

 make a closer examination of the extent to which the so- 

 called Malpighian tubes exist in Amphipods, we find that 

 they occur only in a relatively small number of genera. The 

 majority of these genera belong, as is well known, to the sub- 

 order Crevettina, and Caprella alone constitutes an exception 

 to this ; but the Lsemodipoda must be regarded as belonging 

 to the divergent forms, as is proved by their structure as well as 

 by their mode of life. Among the Crevettina, however, the 

 outgrowths from the posterior process of the mid-gut occur 

 either in forms that live upon the sea-shore (Orc^esfe'a,^^^/^^?/*), 

 or in such as love water that is very little salt {Melita) and are 

 found chiefly in fresh water {Gammarus)^. Since Malpighian 



* It is possible that the freshwater species of the genus Gmnmai-us 



