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Mr. H. N. Moseley on the Anatomy and [Feb. 20, 



The chain of nervous ganglia described as existing in Bipalium 

 (Sphyrocephalus) by Schmarda, and which has been referred to by so 

 many authors, does not exist. There is no doubt that Schmarda mistook 

 the ovaries and testes for ganglia. The real nervous system is ill-defined, 

 but appears to consist of a network of fibres without ganglion-cells, 

 which lies within the primitive vascular canals. In Leptoplana tremel- 

 laris the structure of the ganglionic masses is remarkably complex in the 

 arrangement of the fibres ; and well-defined ganglion-cells of various sizes 

 are present and have a definite arrangement. 



Numerous eye-spots are present in Bipalium, most of them being 

 grouped in certain regions in the head, but some few being found all 

 over the upper surface of the body, even down to the tail. The eye- 

 spots appear to be formed by modification of single cells. In Bhyncho- 

 demus two eyes only are present. All gradations would appear to exist 

 between the simple unicellular eye-spot of Bipalium and the more 

 complex eye of Leptoplana or Geodesmus, where the lens is split up into 

 a series of rod-like bodies, forming apparently a stage towards the 

 compound eyes of Articulata. It is quite probable that these compound 

 eyes have arisen by such a splitting up into separate elements of a single 

 eye, and not by fusion of a group of unicellular eyes, such as those of 

 Bipalium. A peculiar papillary band runs along the lower portion of the 

 margin of the head of Bipalium. The delicate papillae are in the form 

 of half cylinders, ranged vertically side by side. Between the upper ex- 

 tremities of the papillae are the apertures of peculiar ciliated sacs. The 

 papillae, from the mode in which the animal makes use of them, are pro- 

 bably endowed with a special sense-function. The sacs may have a similar 

 office, or they may be in connexion with the primitive vascular system, 

 and have an excretory function ; they may further be homologous with 

 the ciliated tubes in Nemertines. 



In considering the general anatomy of Bipalium, it is impossible to 

 help being struck by the many points of resemblance between this animal 

 and a leech. Mr. Herbert Spencer has, in his 4 Principles of Biology,' 

 placed a gulf between Planarians and Leeches by denoting the former as 

 secondary, the latter as tertiary aggregates, so called because consisting 

 of a series of secondary aggregates formed one behind the other by a 

 process of budding. It is obvious, however, that a single leech is directly 

 comparable to a single Bipalium. The successive pairs of testes, the posi- 

 tion of the intromittent generative organs, the septa of the digestive tract, 

 and, most of all, the pair of posterior caeca, are evidently homologous in 

 the two animals. Further, were leeches really tertiary aggregates, the fact 

 would surely come out in their development, or at least some indication 

 of the mode of their genesis would survive in the development of some 

 annelid. Such, however, is not the case. The young worm or leech is 

 at first unsegmented, like a Planarian, and the traces of segmentation 

 appear subsequently in it, just as do the protovertebrae in vertebrates 



