FISSIPAROUS SPECIES OF TUBICOLAR ANNELID 343 



loosely in it ; the interval between it and the walls of the filament 

 being, I suppose, in continuity with the perivisceral cavity.^ 



The whole of the internal surface of the branchiae is provided with 

 long, close-set, vibratile cilia, while nothing of the sort is visible 

 externally. The end of the stem has a very peculiar structure. It is 

 somewhat enlarged by the development within its walls of a number of 

 elongated granular masses of about yttotj ^^ch. in length, entirely made 

 up of very minute, strongly refracting granules, which, when pressed 

 out, become rapidly diffused and dissolved in the surrounding water. 

 These bodies were not confined to the ends of the branchial stems, 

 but similar aggregations existed at the ends of many of the pinnules, 

 and were also very regularly developed in little elevations seated 

 upon the sides of the stem in front of the base of each pinnule.^ 



Alimentary Canal. — The oesophagus leads into a pyriform, more 

 or less marked, dilatation or crop, provided with thicker walls than 

 the remainder of the alimentary canal (fig. 5). The crop communi- 

 cates by a constricted portion with a wide stomach, whose walls are 

 strongly tinged by deep brown granules. This passes into a narrow 

 intestine, which widens in the caudal region into a sort of rectum, 

 opening externally, between the terminal papillje, by a richly- 

 ciliated anus. 



In every segment the intestine was united to the parietes by 

 delicate transverse membranous dissepiments, forming partitions 

 across the perivisceral cavity, and thus dividing it into a series of 

 chambers, which, so far as I could observe, did not communicate with 

 one another, though it would be unsafe absolutely to affirm this. 



"Vascular" System. — The so-called " blood "-vessels ^ of the 



1 The skeleton of the branchiae of the Serpiilacea has been well and carefully described by 

 De Quatrefages in his valuable memoir " Sur la Circulation des Annelides," Annales de 

 Sciences Naturelles, 1850; and that of Sabella unispira by Grube, so long ago as 1838. See 

 his memoirs "Zur Anat. und Physiologic der Kiemenwurmer." 1838. 



2 Are the peculiar rounded whitish granular patches which occupy a similar position on 

 the arms of Comatula of a corresponding nature, or are these really testes? I have never 

 been able to find developed spermatozoa in them, nor anywhere else in Comatula. 



3 At the last meeting of the British Association (September 1854), I ventured to propound 

 the theory that what are commonly called the blood-vessels of the Annelida are not " blood "- 

 vessels at all ; that is, that these vessels, and the fluid which they contain, are not the 

 homologues of the blood-vessels and blood of Vertebrata, MoUusca, and Articulata, the latter 

 being represented in annelids by the perivisceral cavity and its contained fluid, whose 

 anatomical and physiological importance have been so excellently and exhaustively developed 

 by De Quatrefages. See his researches on the Annelids, and more particularly his memoir 

 " Sur la cavite generale du corps des Invertebres.'' It is to be hoped that M. de Quatrefages 

 understands that instructed Englishmen do not countenance the unwarrantable attempts that 

 have been made to depreciate his merits -in this country. 



