576 THE MICROSCOPE. 



The Ser]nda, if witlidrawn from its calcareous tube (fig. 

 260), is found to have the lower part of the body com- 

 posed of a series of flattened rings, and entirely destitute 

 of limbs or other appendages. Its food is brought to its 

 mouth by currents created by the cilia on the branchial 

 tufts. 



Some of the Annelids are without tubes or cells of any 

 sort, and simply bury their bodies in the sand about the 

 tidal mark. The Arenicola, lob-worm, is a well-known 

 specimen of the class ; its body is so transparent that the 

 circulating fluids can be distinctly seen under a moderate 

 magnifying power. Two kinds of fluids flow through the 

 vessels, one nearly colourless, the other red ; the vessels 

 through which the latter circulate are looked upon as 

 blood-vessels. A few also have not only no tubes but are 

 free and active swimmers. Drs. Carpenter and Claparede, 

 during a sojourn at Lamlash Bay, Arran, met with an 

 interesting member of this class of Annelids, the Tomopteris 

 onisciformis. It possesses a remarkable pair of "frontal 

 horns," projecting laterally from the most anterior part of 

 head, as well as pair of greatly elongated appendages, 

 designated by those observers as " the seco7id antennce,^^ in 

 contradistinction to another and a shorter pair of appen- 

 dages situated just in advance of them, the first pair 

 being characteristic of the larval, and the second of the 

 adult state of the annelid. 



" The head also bears on its dorsal surface a pair of 

 ciliated epaulettes^ which extend over the edges of the 

 bilobed nervous ganglion. These, at a certain stage of 

 development, are fringed with long cilia both at their 

 margins and their base ; but as the cilia are only occa- 

 sionally to be seen in activity, they may escape the atten- 

 tion of the observer. Cilia are likewise distinguishable on 

 certain parts of that innermost layer of the general integu- 

 ment which forms the external boundary of the peri- 

 visceral space, and by their agency a special movement is 

 imparted to the corpuscles of the fluid contained in. the 

 cavity." 



The development of the caudal prolongation is peculiar, 

 and this as w^ell as other points of interest are given 

 in the Lin. Soc. Trans, vols. xxii. and xxiii. pp. 335 



