LIFE OF RELATION. 31 



muscles) are composed of very distinct fusiform nucleated cells, entirely resembling the muscle- 

 cells of the involuntary fibre in the higher animals. 



The existence of striated fibre in the Polyzoa was first noticed by Milne-Edwards, who 

 detected it in Eschara ;* and Mr. Busk has since described and figured the same form of 

 tissue in Anguinaria spatulata, Nofamia hursaria, and other marine Polyzoa. t 



(5.) Organs of the Life of Relation. 



I have succeeded in making out a distinct nervous system in all the genera with the 

 exception of Urnatella and Pectinafella, which I have had no opportunity of examining, and 

 of PahuliceUa, in which I have not as yet been able to efi'ect any satisfactory demonstration 

 of its existence. In the phylactolfematous species, there may be seen attached to the external 

 surface of the oesophagus, on its rectal aspect just below the mouth, an oval body of a yellowish 

 colour, and presenting a somewhat lobed outline (PI. II, fig. 24; V, fig. 5 ; IX, fig. 7, ic). 

 That it is a nervous ganglion there cannot be any doubt, and I have succeeded in distinctly 

 tracing nervous filaments in connection with it. In Cristafella, Lophopus, and other genera with 

 crescentic lophophores, the ganglion may be seen giving off from each side a rather thick 

 chord (PI. II, fig. 24, x) which immediately enters the tubular arms of the lophophore, and then, 

 after giving off a branch which runs along the root of the lophophore towards the hsemal side, 

 and which sends in its passage a filament to each tentacle on this side of the lophophore, it 

 continues its course {x) along the roof of the arms to their extremity, sending off at regular 

 intervals a filament to each tentacle upon the outer margin of the arm. When it arrives 

 at the extremity of the arm it turns on itself, and in its retrograde course gives off similar 

 filaments to the tentacula placed upon the inner margin. I have thus traced it back to the 

 base of the arms, but have here failed in my attempts to follow it further ; it is, however, 

 highly probable that it passes across the lophophore to unite with the corresponding chord of 

 the opposite side. The tentacular filaments are directed towards the intervals between the 

 tentacula. The ganghon also sends off a filament {ij), which dives into the substance of the 

 oesophagus just behind the mouth ; it is probably distributed to this tube, and to the mouth and 

 epistome, but I have not succeeded in detecting anything like a nervous collar surrounding the 

 oesophagus at this place. There is no other ganglion than the one just described ; and, unless 

 it be the epistome, and possibly in PedicelUna a peculiar ciliated organ J in the neighbourhood 

 of the ganglion, nothing which can with any real probability be referred to an organ of 

 special sense has as yet presented itself in any polyzoon. 



* Milne-Edwards, Recherclics Auatomiques, Physiologiques et Zoologiques sur les Eschares, 

 ' Ann. des Sci. Nat.,' 2de serie, t. vi. 



f Busk in 'Transactions of the Microscopical Society of London,' vol. ii. 

 X See note, p. 19. 



