520 HENRY M. BERNARD, 



of the pedipalps, coxal glands and tracheœ in the céphalothorax ; 

 book-lungs or trachea; and the spinning glands in the abdomen. This 

 row forms a striking parallel to that just described occurring along 

 the lateral line of other Tracheata. The question is : are they homo- 

 logous structures both with one another and with the corresponding 

 row in the Hexapoda, or, in other words, can they be referred to 

 setiparous or acicular glands of the original Tracheatan-Annelid ? The 

 parallel between the lateral row in the Hexapoda and the ventral row 

 in the Arachnida is so remarkable that, without yielding to any un- 

 due love of symmetry, it is difficult to avoid the conclusion that they 

 must be related structures. The closeness of the parallel is only 

 disturbed by the much debated coxal glands in the Arachnida; 

 these seem to have nothing corresponding to them in the lateral 

 rows of the Hexapoda. In the present article I shall therefore leave 

 the coxal glands out of consideration, merely remarking that so great 

 an authority as Eisig ^) believes them to be modified setiparous 

 glands, and that my own researches, as far as they go, tend 

 to confirm this view. If this prove correct, the ventral row of homo- 

 nomous structures in the Arachnida is complete. 



If we assume that the parapodia of the original Annelid had. both 

 dorsal and ventral branches, each with its aciculum, we might then 

 perhaps assume that in the Hexapoda the dorsal row of acicular 

 sacs, in the Arachnida the ventral row became specialised along 

 somewhat similar lines in adaptation to new methods of life. It 

 were now perhaps vain to speculate on the original cause of this 

 interesting difference. A parallel , however , between Peripatns and 

 the Arachnids is at once suggested. In both these animals the row 

 of glands to be deduced from setiparous sacs is ventral. On the 

 other hand, the two are in striking contrast; in Peripatus the tracheae 

 are diffused, and may be assumed to be the sacs of scattered bristles, 

 while in the Arachnida the trachea'- are confined to the ventral rows 

 before mentioned, the animals themselves being, as a rule, richly 

 covered with bristles. 



Taking these ventral structures in order, we have the glands of 

 the chelicera' generally admitted to be setiparous glands'*). The 

 maxillary glands have all the appearance of being a cluster of seti- 

 parous glands, judging from Schimkewitsch's drawing^). Passing 



1) Die Capitellirlen des Golfs von Neapel, pp. 393, 400. 



2) KoRSCUELT und Heider, Eßlwicklungsgeschichte, p. 608. 



3) Étude sur l' anatomie de l' Epeire. in : Ann. Sc. Nat. 1884. 



