540 F. W. GAMBLE AND J. H. ASHWORTH. 



tions by Max Schultze^ Horst, Ounningham^ and others, of 

 the development of A. marina have not been made from 

 eggs and larvse which indubitably belong to this species or 

 even genus. While, if Mesnil is right in regarding Bran- 

 chiomaldane as an Arenicolid, its development is entirely 

 without metamorphosis, judging from his description and 

 figures.^ 



The following statement contains a summary of the charac- 

 ters of the genus and species (Woodcut, p. 542). 



Arenicola. 



Limnivorous Polychasta provided with numerous pairs of 

 branched gills, not present on the anterior seven segments. 

 Prostomium small or moderately well developed, bounded 

 posteriorly by the nuchal organ. There are no tentacles or 

 palps. Parapodia consisting of transversely thickened neui'o- 

 podia, each bearing a vertical row of crotchets, and of conical 

 notopodia bearing setas. In the chjetigerous region of the 

 body, except in the first three segments, there are four 

 annuli between successive chaetigerous annuli. Internally 

 there are three strong diaphragms at the anterior end of the 

 first, third, and fourth somites. There is no armature to the 

 pharynx. A pair of hearts places the gastric vessels in 

 communication with the ventral vessel. There are five, six, 

 or thirteen pairs of uephridia. A pair of peristomial otocysts 

 present except in A. Claparedii. 



I. A distinct tail present, the parapodia and gills not 

 extending to the posterior end of the animal. The body is 

 often swollen anteriorly. Gills pinnate or derivable from 

 pinnate type, eleven to thirteen pairs, the first gills (some- 

 times small) on the seventh chaetigerous segment. Well- 

 marked prostomium consisting of a median and two lateral 

 lobes. Brain well developed, with anterior, middle, and 

 posterior lobes. 



Nephridia with dorsal lip well provided with flattened 

 spatulate ciliated vascular processes ; ventral lip ciliated 

 » Mesnil (1898), p. 636, figs. 1—5, 



