112 ARACHNIDA. 



Acarina — Croneberg). It should be noted that, according to 

 Schimkewitsch, the so-called lower lip also arose from a similar 

 paired rudiment, but in this case a pair of limbs seems out of the 

 question. 



If such a vestigial pair of cephalic limbs is really present, it 

 must be regarded (Croneberg, Jaworowski) as the missing antennae, 

 and would be homologous with the first antennae of the Crustacea. 

 This would necessitate no essential modification of our view. The 

 first antennae, which were present in the ancestors, would still occur 

 in the Araneae as vestiges, the chelicerae, however, corresponding 

 to the second antennae. 



The pedipalps were compared by us with the mandibles of the 

 Insecta. Each is composed of a masticatory ridge and a many- 

 jointed palp. In the embryonic rudiment, however, both parts are 

 said to consist of a number of joints ; if so, this limb would show a 

 very primitive character, and a certain agreement with the biramose 

 extremities of the Crustacea (Jaworowski). Indications of this 

 biramose character are said to be found in the rudiments of other 

 limbs also (Jaworowski). 



Further, whichever pair of limbs (chelicerae or pedipalps) is 

 compared with the mandibles of the Insecta, the many-jointed 

 character of the Arachnid limb affords a significant contrast to the 

 Insectan mandible, which always consists of a single joint. Another 

 primitive character is found in the presence of masticatory blades on 

 the third and fourth limbs (in the Scorpiones and Opiliones), these 

 extremities being thus partly utilised as mouth-parts, like the 

 thoracic limbs of Limuhis which surround the mouth. The presence 

 of pincers on the anterior limbs might also well be regarded as 

 primitive, since such pincers are found in Limulus. We do not, 

 however, lay any great stress upon this, as similar structures may 

 arise independently of each other. 



The condition of the cephalo-thorax and its appendages in the 

 various divisions of the Arachnida shows far more agreement with 

 those of the Insecta than is found in the next section of the body — 

 the abdomen — even if Ave overlook the reduced conditions which are 

 exhibited here in the Acarina. We must here mention that the 

 Solifugae, owing to the fact that the three posterior cephalo-thoracic 

 segments are free, while the anterior region becomes swollen in a 

 manner sucrsjestive of a head, have a certain resemblance to an insect. 



DO ' 



In addition to this, the abdomen shows the same number of segments 

 as in the Insecta, and a pair of stigmata appears on the first 



