TRANSACTIONS OF SECTION D. 473 



tail. There are twenty-four main trunks in all, four branches from each nerve. 

 The blood-vessels are derived from the caudal aorta and vein. Lymphatics are 

 also found. The main trunks of the sympathetic which accompany the aorta 

 can be traced for some distance into the regenerated tail and send branches to 

 the different blood-vessels. No new ganglia are formed. 4. In the centre of 

 the tail is a tube of cartilage, unsegmented and continuous except for some 

 perforations through which blood-vessels pass to the interior. This tube is 

 continuous with the body and neural arches of the vertebra through which the 

 fracture has taken place. 5. In the cartilage tube is an epithelial tube con- 

 tinuous with the central canal of the spinal cord. 



On examining tails in various stages of regeneration we find the following : 

 The wound after autotomy is quickly covered with new skin beneath which is 

 a mass of spindle cells which apparently originate in the connective tissue. 

 This cellular mass acts as a growing point, to the new tail, and from it the 

 various structures are developed. The cartilage, fat, and blood-vessels arise by 

 differentiation from the spindle cells. The muscle fibres arise segmentally in 

 groups, the groups nearest the tip being the least differentiated. The muscles 

 in the stump play no part in the process. 



The nerve trunks involved in the autotomy-wound elongate as the regenera- 

 tion proceeds. The corresponding posterior root ganglia are increased in size 

 or number owing to increase in size of the nervo bundles. There is no increase 

 in size or number of the ganglion cells. 



The central canal reaches to the extreme tip of the tail just beneath the 

 skin. It there loses itself in the surrounding cells and is apparently developed 

 from them. It has no connection with the epidermis. 



The Geographical Distribution of the Pennatulacea. 

 By Professor S. J. Hickson, F.R.S. 



8. Exhibitio)i of Specimens in the Zoological Laboratories of the 



University. 



FRIDAY, SEPTEMBER 10. 



The following Papers were read : — 



I. Account of the Plankton collected during Traverses of the Great 

 Oceans on the journey to Australia and back, by several routes, 

 in 1914. By Professor W. A. Hebdman, F.R.S., and Andeew 

 Scott, A.L.S. 



Advantage was taken of the meeting of the British Association in Australia 

 last summer to obtain samples of surface plankton collected continuously dxiring 

 traverses of the North and South Atlantic, the Southern Ocean, the Indian 

 Ocean, the seas of the Malay Archipelago, and the Pacific. The method of 

 collecting was that made use of by one of us on several previous occasions, and 

 which con.sists briefly in letting the sea-water which is pumped continuously 

 into the ship flow out from a bath- or other tap through a fine-meshed silk net, 

 which is changed morning and evening — so that each sample obtained repre- 

 sents a twelve hours' catch, either day or night. The silk used was No. 20 of 

 Dufour's series, having about 6,000 meshes to the square centimetre. 



Small samples of each gathering were examined somewhat rapidly with the 

 microscope while fresh, and any special organisms and colours were noted. The 

 whole was then preserved in a solution of formalin. 



The outward voyage on the Blue Funnel liner Ascanius was by the Cape 

 route, so that the 72 samples collected represent a traverse from Liverpool 



