TRANSACTIONS OF SECTION D. 



779 



this country to patlier tlic native woods together into one collection on a scale 

 commensurate with the extent of the new continent and the importance of its 



forests. 



7. 0)1 the Structure and Development of Loxosonia, 

 liy Sidney P. Hakmer, B.A., B.Sc. 



Tlie i!cr\(ins and exci'etorv systems of the adult were investigated specially in 

 I, cnisMcuuda , in tlie living condition or by means of glycerine ])re])aral iuns. 



1. The ffCDii/lioH, situated between mouth and anus, has been frequently figured 

 in previous papers on Lo.rofoma, but has hitherto invariably been wrongly 

 idtiititied as some part of the generative system. It is a dumb-bell shaped organ, 

 developed in the bud from ectoderm, and giving oil" at its two ends nerves to the 

 tiiiticles and other parts of the body. The ectoderm contains numerous sense-colls, 

 Ijea.'ing one or more long .stifl' t act ile hairs prqjectiug into the water. Each sense- 

 f?;iis directly connected with the nervous system by means of a singlti fine nerve 

 nbvil. swelling into a bipolar ganglion cell at some part of its course. 



2. The excretory system consists of a pair of tine tubes, ciliated internally, and 

 c impojifd of a small number of large perforated cells, the ])ro.\imal cell being in all 

 |i:akbility a flame-cell. There is no ciliated funnel, the excretory organ ending 

 blindly near the ventral wall of the stomach. Each tube opens independently into 

 the vestibule, Ijetween mouth and anus. The nepbridia oi Lo.v<i.f<imit thus diil'ei 

 miirkedly in structure; from those of Braehiopoda or Phoronis, but resemble in 

 a striking manner the head kidney of Annelid larvte, as well as the permanent 

 iiephridia of Rotifers and I'latyhelminths. 



0. Tlie development of Ln.nisoina has been studied by means of sections in a 

 species, probably hitherto undescribed, occurring on LcptdcUnuin in the (iidf of 

 Naples. 



The ' dorsal organ ' is not developed from hypoblast cells, as stated by Hatschek 

 m Pedicel linn (' Zeitschr. f. wiss. Zool.,'lM. xxix. 1877, S. 502),but, on the contrary, 

 entirely from the epiblast. An epiblastic invagination is formed, but soon loses its 

 lumen, then appearing as a solid crescent-shaped mass of cells, applied to whose 

 deeper surface is a conspicuous mass of fibrous tissue. The 'dorsal organ' bears 

 two large eyes, and is in all probability the brain or supra-asophageal ganglion of 

 the larva. The permanent ganglion of the adult is hence infra -oesophageal, and the 

 line between mouth and anus is ventral. 



The ' dorsal organ' takes no part in the budding of the larva, which after a free 

 life of some hours may be seen to have developed a pair of lateral buds, one on 

 each side of the ' dorsal organ,' but at a level intermediate between this structure 

 and the ciliated ring. The alimentary canal appears to atrophy during the budding, 

 and it is hence probable that the larva dies after the producticm of two or more 

 buds. It is doubtful whether the larva ever permanently fixes itself, or whether 

 the budding takes place normally during the free life of the larva. 



4, The Entoproctous Polyzoa conform perfectly in structure to the TrochospJuere 

 type. This view is much strengthened by the study of their excretory organs. The 

 results of tlie present investigatioir seem to show that the Polyzoa have their 

 nearest adult allies in the Hotifera, whilst they have but little in common with 

 Brachiopoda or Phoronis. 



?. On Anatomical Variations : (1.) Far-occipital Process occurring in Man, 

 {-.) Secondary Astrarjalns. (3.) Persistence of the Left Duct of Cuvler 

 in Man. By Professor Shepherd, M.D. 



1. Par-occipital Process in Man. — The skull of an Irish navvy, aged about 

 tliirty years, was exhibited, in which there was a well-marked par-occipital process. 

 Left jugular process of occipital bone, prolonged downwards to articulate with 

 tlie transverse process of atlas, length, 2 cm. ; diameter, 1 cm. In the same skull, 

 on same side, the styloid hyoid ligament was ossified and articulated with the hyoid 

 lone— length, 0-2 cm. ; diameter, 3 cm. 



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