Trachece from Setiparous Glands. 27 



vary gland, nevertheless correctly described its different 

 appearance in different Galeodidee. In some it is a simple 

 long tube commencing in the region of the second leg, 

 running backward to form a tangled coil between the nerve- 

 cords in the region of the third and fourth legs. It then 

 bends forward again to open in the above-mentioned spot. 

 In others the proximal end of the gland divides up into a 

 sponge-like mass of anastomosing tubules, which, uniting with 

 those of the gland on the opposite side, form an amorphous 

 mass arching over the mid-gut. The course of the duct and 

 the position of the aperture agree almost exactly with that 

 described by Sturany for the coxal gland of Atypus. 



The points which especially interest us liere, however, are 

 the following. The aperture of the gland on the coxa of the 

 first leg agrees almost exactly in position with the aperture of 

 the trachese on the coxa of the second leg, which suggests 

 their being homologous structures. The duct shows the 

 characteristic striped appearance, as if its wall were pitted by 

 countless pores. It stains very badly, and although it will 

 not stand boiling in caustic potash, resists the action of cold 

 caustic potash. There seems to me to be little doubt that 

 chitin is present in its walls, although it nowhere forms a 

 definite lining to the tube. The retention of the gland in 

 Gahodes as an important functional excretory organ, while it 

 has degenerated in the Araneid^e, although once well developed 

 in these latter, suggests a correlation between these coxal 

 glands and the spinning-glands. The development of the 

 spinning-glands to utilize and carry off excretory products 

 renders the coxal glands unnecessary. This correlation is 

 the more probable if both glands can be referred back to 

 setiparous glands. The same may be said of the mandibular 

 poison-glands, which are well developed in the Araneids, but 

 absent in Galeodes. 



Besides the fact mentioned in my first contribution on this 

 subject, that no difference can be discovered between the 

 trachea3 of the thorax and of the abdomen, it also remains to 

 be stated (what indeed has been known since 1848 *) that 

 the trachege of the two regions communicate freely with one 

 another. The assumption that the abdominal tracheae are 

 developed from lung-books while the thoracic tracliese are 

 independent developmentsf from ectodermal invaginations, and 

 therefore not in any way homologous with the former, seems 



* Kittary, " Anatomisclie UntersucliuDgen der gemeinen Galeodes und 

 der fiirclitloseu Soljmffaj" Soc. Imp. Moscou, vol. xxi. 

 ^t Korschelt and Heider, * Vergleicliende Eutwickelungsgeschichte,' 

 p._638. 



