Branchiomaldane vincenti 153 



The lobate brain, oesophageal connectives, non-ganglionated nerve- 

 cord (without giant fibres), and eyes are similar to those of a young 

 Arenicola. Statocysts are absent. 



The earlier statements regarding the nephridia of 1>. vincenti 

 give the impression that there is considerable variation in the number 

 of these organs. Prof. Mesnil (1897) referred to the presence of 

 pigmented segmental organs in the 5th, 6th, 7th and 8th chae- 

 tiferous segments, and, in 1898, stated that four or five pairs were 

 present ; Prof. Fauvel attributed three to five pairs of nephridia to 

 this worm, but Drs. Gamble and Ashworth found only two pairs, 

 opening on the fifth and sixth segments. The writer has examined 

 five specimens in regard to their nephridia, and in all of them 

 only two nephridiopores could be seen, situated immediately ventral 

 and posterior to the fifth and sixth neuropodia. By means of 

 serial sections of two specimens and by dissection of another it has 



N.O.' 



X 90 



Fig. 66. B. vincenti. Diagram of the nephridia of the left side, seen from the inner (median) aspect. 

 The crotchets of the fifth, sixth, seventh, and eighth neuropodia (v, vi, vn, Vlll), and the 

 external openings (N.oi, N.O 2 ) of the first and second nephridia 1 are indicated. 



been proved definitely that only two pairs of nephridia are present 

 but the second is continued backwards, beyond its pore, as far as 

 the eighth or ninth neuropodium, where it ends blindly (Fig. 66). 



The gonads are situated on the coelomic epithelium, especially 

 of the oblique muscles and septa. All the specimens examined by 

 the writer were hermaphrodite. The oocytes fall into the coelomic 

 fluid at an early phase of growth ; their later growth-phases are found 

 chiefly in the posterior segments, the coelomic cavities of which, in 

 mature specimens, are practically filled with large oocytes (Fig. 67). 

 When fully mature the eggs are, according to Prof. Mesnil, milk- 

 white and about *3 mm. long and *2 mm. broad. They are thus 

 considerably larger than those of any species of Arenicola, and taking 

 into account the sizes of the parent worms, the eggs of Brancliio- 



1 The funnels of the nephridia, which are small and difficult to investigate 

 in preserved material, are apparently simple, but their structure can be 

 determined satisfactorily only in living specimens. 



