60 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL.97 



concludes that the anterior part of the brain, lying before the antennal 

 commissure and bearing the optic lobes, represents the prostomial 

 archicerebrum of the annelids, and that the rest of the brain is of 

 postoral origin, being formed of the united anterior ends of the 

 nerve cords extended secondarily in front of the stomodaeum. This 

 alleged postoral part of the definitive brain, Fedorovv believes, 

 includes the ganglionic centers of the antennal somite, and the ganglia 

 of a reduced premandibular somite that has lost its appendages. The 

 jaw centers, he contends, are contained in the parts of the nerve cords 

 immediately behind the brain, from which arise the nerves of the jaw 

 muscles (/), and which are connected by the first postoral commissure 

 (iCom). Fedorow's elaborate analysis of the brain structure and 

 nerves would be more convincing if it took into account the embryonic 

 development of the brain; his results are entirely unsupported by 

 ontogenetic evidence, and are mostly at variance with observations on 

 the brain development reported by other investigators. 



The internal structure of the onychophoran brain (fig. 26) shows 

 fundamental characters of the polychaete brain, and contains certain 

 arthropod features, but it presents also special modifications that are 

 not found in either the annelids or the arthropods. Corpora peduncu- 

 lata are well developed, each consisting of a cap of three globuli (Gb) 

 of small chromatic cells lying in the anterior part of the brain, and 

 of a large pedunculus (Fed) composed of three confluent groups of 

 fibers springing from the globuli cells. The sensory antennal nerves 

 (AntNv) coming into the anterior angles of the brain traverse the 

 upper part of the cerebrum in distinct antennal tracts (AntT), which 

 are united posteriorly in a broad antennal commissure {AntCoin). 

 The association centers of the antennal nerve fibers, called by Holm- 

 gren (1916) and Hanstrom (1928, 1935) the antennal glomeruli 

 (AntGlni), lie laterad of the anterior ends of the corpora pedunculata, 

 and are said by Hanstrom to be closely connected with neurites of 

 the globuli cells. In this feature, Hanstrom points out, the Ony- 

 chophora have a distinctly polychaete character in the brain structure, 

 since the antennal glomeruli of the onychophoran brain evidently 

 correspond with the palpal glomeruli of the polychaete brain (fig. 

 18 B, F, PlpGlm). On the other hand, the onychophoran brain shows 

 arthropodan characters in the presence of a well-developed central 

 body {Co) and an antennal commissure (AntConi) . But again, the 

 small optic lobes of the eyes (fig. 25 A, OpL) contain each only a 

 single ganglionic center, while all arthropods have at least two. The 

 optic ganglia are connected with the corpora pedunculata and with 

 the central body. 



