Branchiovialdanc vincenii 155 



ment of this worm (Fig. 68). He states that the " embiyo " remains 

 in the egg-membrane np to an advanced stage of development, 

 finally becoming strongly flexed. When it becomes free, the young 

 worm has two pairs of eyes and several segments, of which the third, 

 fourth, fifth and sixth bear dorsal capillary chaetae, but not crotchets. 

 Cilia were not visible except at the posterior dorsal margin of the 

 prostomium, that is, in the nuchal groove. 



Through the courtesy of Trof. Mesnil the writer has been enabled 

 to examine the three original specimens of " Clymenides incertus'' 

 which are about 2 * 5 mm. long, and he has no hesitation in stating 

 that they are young phases of B. vincenti. . A comparison of the 

 capillary chaetae (Figs. CI, 02) of " C. incei^tus" with those of 

 B. vincenti shows that they are all growth forms of the same type of 

 chaeta, and the neuropodial crotchets (Figs. 63, 64) present identical 

 characters. Other important points of agreement are afforded by 

 the prostomium, the segmentation of the body and the absence of 

 statocysts. 



Systematic Positiox. — BrancliiomaldaneiB more nearly related to 

 Arenicola than to any other Polychaete and must be included in 

 the family Arenicolidae, but the writer is of opinion that the union 

 of the two genera Brancliiomaldanc and Arenicola, recommended by 

 Prof. Fauvel, is not advisable. Prof. Fauvel has pointed out that 

 Branchiomaldane presents several points of resemblance to a young 

 A. ecaudafa, but it may be noted in this connection that, as these 

 worms live under practically identical conditions, some of the 

 similarities may be due to convergence. Further, some of the resem- 

 blances cited by Prof. Fauvel are not so close as they were believed 

 to 1)6 ; compare, for instance, tlie nephridia and the position of the 

 gills in Branchiomaldane and Arenicola. It is also worthy of note that 

 in the most nearly related species of Arenicola, namely, A. ccandata 

 and A. hrancliicdis, there are well developed statocysts and septal 

 pouches, which are wanting in Branchiomaldane. Other important 

 characters presented by Branchionicddanc — the occurrence of herma- 

 phroditism, the extensive distril)ution of the reproductive organs on 

 the oblique muscles and septa, the production of comparatively 

 few, large and plentifully-yolked eggs, which do not give rise to 

 free swimming ciliated larvae — are not paralleled in Arenicola. 

 The striking differences in the branchiferous segments — which are 

 bi-annulate in Branchiomaldane, the setae and gills being borne on 

 successive aunuli, while in Arenicola they are subdivided into five, 



