322 SUMMARY OF CURRENT RESEARCHES RELATING TO 



heap contained from twelve to fifty fruits, some lying loose, some partly 

 buried, and bound together with earth and a few fibres, probably grass. 

 The ground for a radius of several inches round each heap was markedly 

 free from seeds and clean, so that it seemed as if the earthworms had 

 reached out as far as possible and dragged back all the seeds they could 

 find to the mouths of their burrows. In every collection, three, four, 

 or more seeds had sprouted, while outside the heaps not a single sprouting 

 seed was found. Several weeks later some dozens of young trees, three 

 or four inches in height and with two or three pairs of leaves, were found 

 under the parent trees, standing, with the remains of the heaps still 

 visible about them, apparently on the site of the earthworms' burrows. 



Systematic Position of Chsetognatha.* — R. T. Gunther concludes 

 that this class approaches in its structure and development nearer 

 to the Mollusca than to any other group. He points to the following 

 resemblances : — the worm-shaped body, which recalls the Amphineura 

 Aplacophora ; the bilateral symmetry in general, and particularly of the 

 body-cavity ; the presence of an abdominal sac behind the anus ; the 

 absence of undoubted segmentation ; the jaw armature in Sagiita and 

 Proneomenia ; buccal and visceral commissures in the nervous system ; 

 the pre-oral ciliary wreath or velum ; the endoskeleton in the head of 

 Nautilus and Spadella ; the lateral and tail fins in Sagitta and the 

 Dibranchiate Cephalopods ; the two paired openings from the cavity 

 of the gonads ; the hood and the circumoral propodium of Cepha- 

 lopods ; the development of the eggs within a follicular epithelium 

 and their growth upon stalks ; the tendency in pelagic molluscs for 

 shell, mantle, gills and foot to disappear, e.g. PhylJirho'e. On the 

 ground of these and other observations, Chajtognatha are regarded as 

 the living representatives of that phyletic stage which is represented 

 by veliger larva?, and from such a free-swimming ancestor the creep- 

 ing Polyplacophora, worm-shaped Aplacophora, and the swimming 

 Cephalopods may have arisen independently. A systematic scheme of 

 the Mollusca is put forward in which Chastognatha and Cephalopoda are 

 grouped together as Nectomalacia, and all other Molluscs as Herpeto- 

 malacia. The characters of these groups are defined. 



Nematohelminth.es. 



Nervous System of Ascaris.t — D. Deincka describes the sensory 

 and motor nerve-cells. He recognises two types of sensory cell. Those 

 of the first type are connected with each other by means of their short 

 processes, along which the neurofibrils of one cell pass over into the body 

 of another, and also by means of central processes which, branching greatly 

 as they meet, form an intimate network. The cells of the second kind 

 are connected by means of short, greatly branched dendrites. The two 

 kinds of cell are closely intermingled in the sensory end apparatus ; they 

 share by means of their fibrils in the formation of the thin nerve-tufts 

 of the papillae, and also form the network of delicate nerve-branches 

 which constitutes the main mass of the papillae The motor-cells are 



* Zool. Anzeig., xxxii. (1907) pp. 71-2. 



t Zeitschr. Wiss. Zool., lxxxix. (190S) pp. 242-307 (9 pis. and 7 figs.). 



