58 Mr. H. M. Bernard on the 



tlie Crustacean gland would then be, what it clearl}' is in 

 Galeodes, a development of the proximal end of an originally 

 simple tubule, and not, as is often suggested, a modified 

 portion of a primitive coelom. 



The establishment of this point would be one more argu- 

 ment in favour of ray view that the antennal and shell-glands 

 of the Crustacea are probably derivations of acicular or seti- 

 parous glands*. It is interesting to note that a similar sugges- 

 tion had already been made by Eisig f with regard to the 

 origin of the coxal glands of the Arachnids. 



In both cases {i. e. in Crustacea and Arachnida) we should 

 then have setiparous glands gradually specialized for excretory 

 purposes as the primitive nephridia became specialized into 

 genital ducts. The extreme plasticity of the setiparous glands 

 is well known — slime-glands, spinning-glands, and poison- 

 glands being generally deduced from them ; further, tracheal 

 invaginations and salivary glands may also with great proba- 

 bility be traced back to them. That some of them should 

 have become specialized for excretion is not improbable. 



Without enlarging any further on this suggested deriva- 

 tion of the antennal and shell-glands of the Crustacea and the 

 coxal glands of the Arachnida from setiparous sacs, I should 

 like to point out a remarkable physiological connexion Avhich 

 appears to exist between the different kinds of Arachnidun 

 glands. Galeodes has no spinning- or poison-glands, but 

 highly developed coxal glands and Malpighian vessels. 

 hcorpio has well-developed stinging-glands, which, however, 

 are but occasionally employed, and well-developed coxal 

 glands and Malpighian vessels. The Chernetidaj have very 

 large true spinning-glands and modified spinning- (cement-) 

 glands, which are periodically developed. They have, further, 

 coxal glands, but no Malpighian vessels. In these animals 

 we have to bear in mind that the spinning- and cement-glands 

 are not always functional, so that some purely excretory 

 apparatus for the direct removal of waste products is required 

 during those times when these excretory matters are not being 

 utilized for the formation of silk or cement. 



In the Araneidai we have, as a rule, a perennial flow of silk 

 and a consequent degeneration of the purely excretory glands. 

 The coxal glands have, as a rule, degenerated, wltnle the 

 Malpighian tubules no longer come in contact with the blood- 

 stream, but ramify through the peritoneal cells which bind 

 the numerous diverticula of the mid-gut into a solid mass, 



* ' The Apodidfe ' (MacmiUan, 189i'). 



t Eitig, 'l)ie Capitelliden des Goltes vuii Xeapel' (1867). 



