THE INTERXAL STRUCTURE OF ANTS. 57 



queen ant is a degenerate creature like the queen bee. In future chap- 

 ters of this work I shall have occasion to show the untenability of this 

 supposition in the light of recent observations. 1 



The foregoing considerations do not, of course, invalidate Dujarclin's 

 hypothesis. It is also true that the conditions' throughout the insect 

 class point to a direct correlation between the development of the 

 pedunculate bodies and the instinctive activities, but a study of these 

 structures in other Arthropods is not so unequivocal. Turner, in a 

 contribution from my laboratory (Zoo/. Bull., II, 1899, pp. 155-160), 

 showed that the pedunculate bodies not only occur in Crustacea ( Cain- 

 barus) and the king crab (Linniliis), but also in annelids (Nereis, 

 Lepidonotus, Polynoe), and that they reach their greatest development 

 in the king crab. In this animal they are a much-branched mass, which 

 forms the bulk of the brain, and as Turner says, " simulates in struc- 

 ture the vertebrate cerebellum." On Dujardin's hypothesis we should 

 therefore expect the king crab to be the most intelligent of arthropods. 

 But although no one will deny that this animal has had ages in which 

 to acquire a high psychical endowment, it shows no signs of having 

 profited by its opportunities. It would seem, therefore, that the pedun- 

 culate bodies must be subjected to a more critical morphological and 

 physiological study before they can be accepted as the insectean ana- 

 logue of the human fore-brain. 



The Ventral Nerve-Cord. Although the subcesophageal ganglion, 

 like the brain, consists of three fused ganglia, these have become less 

 modified and are clearly discernible in sagittal sections (Fig. 27). The 

 rule that each ganglion of the central nervous system innervates only the 

 segment in which it originated in the embryo also holds good of the 

 subcesophageal ganglion. We find that it sends off three pairs of nerves, 

 containing both motor and sensory fibers. The first pair ( ;/;// ), which is 

 stouter than the two others, innervates the sense organs and muscles of 

 the mandibles, and the second (nin.v) and third ( /;/ ) the corresponding 

 parts of the maxillae and labium respectively. The three thoracic ganglia, 

 owing to the voluminous and complicated leg and wing muscles which 

 they innervate, are much larger than the abdominal ganglia. Each gives 

 off a pair of crural nerves to the legs and. the prothoracic ganglion also 

 supplies a chordotonal organ near its antero-ventral end (clw). From 



1 Comparison of my figures of L. brci'iconris with Forel's of L. fuligiiiosiis 

 reveals the fact that the female brain of the latter species is no larger than that 

 of the worker, whereas in brevicornis there is a slight difference in size in the 

 corresponding phases. It appears from recent observations of De Lannoy (1908) 

 and Emery (1908) that the queens of L. fuliginosus are but little larger than tilt- 

 workers and are probably temporary parasites (see Chapter XXIV). This may 

 at least partially account for Forel's finding the brain of the female ant inferior 

 in organization to that of the worker. 



