224 THE APODID^ part ii 



bites. In the second of these they are cut through 

 along the Hne shown in Fig. 53. These transverse 

 sections through the head and labrum certainly seem 

 to indicate the presence of such antennae as we have 

 described, at least they seem to show that there were 

 appendages of som^e sort starting out sideways from 

 each side of the labrum, just as in Apus. It is 

 perhaps possible to interpret all these fragments of 

 limbs shown in the sections, both those seen springing 

 from the sides of the labrum, and those scattered about 

 the section, as parts of the limbs of the hind-body, 



>} 



Fig. 51. — Sections through Ceraurus pleurexantheinus (after Walcott) passing througli 

 the prostomium, showing traces of liml:)s springing out from each side of the 

 same, which we assume to be homologous with the antenna; of Apus ; the 

 fragments of limbs at the sides may be those of trunk limbs brought near the 

 mouth by the rolling up of the aninaal. 



which when the animal is rolled up are naturally 

 brought up to the mouth. This, however, does not 

 seem to be so probable as our supposition, founded 

 upon a comparison with Apus, that those actually 

 starting from the sides of the prostomium are traces 

 of true antennae, because : 



(2.) We think that, if the place assigned by 

 Walcott to the three posterior head limbs is correct, 

 some form of aiiteiincs nutst have been present, if not as 

 antennae then as mouth parts of some kind. Accord- 

 ing to our theory, one of the chief advantages of 

 the bending round of the anterior segments was the 



