.APHRODITA ACULEATA. 257 



Milnesia borealis (Johnst.) is only the young of A. aculeata in a somewhat imperfect con- 

 dition. 



Grube was of opinion that the A. sericea of Savigny, and A. borealis, Johnst., refer to 

 this species, and that Risso's form, A. aurata, is the young of the same. 



Claparede l describes the peritoneal coat of this species as being the most distinct 

 example in the group, and he figures the fine stride which characterise it. At 

 intervals on this surface he found groups (mouchets) of vibratile cilia as in Hermione, 

 and as Sharpey had long previously observed. He alludes to the ovaries which he found 

 on the ventral surface at the bases of the feet. They were in bands (boyau) in the 

 median line attached to a cord. He could not satisfy himself as to the nature of this 

 cord. He further points out the peculiar structure of the papillae, the bases of which can 

 be traced to the interior of the palpi. He differs from De Quatrefages, who states that the 

 first two pairs of ganglia are completely separated from their homologues of the other 

 side. He considers that these ganglia do not exist ; they are simply the inferior part of 

 the oesophageal connectives. 



A good account of the distribution of the blood-vessels of this species is given by 

 Prof. E. Selenka. 2 He describes in injected specimens a dorsal and a ventral vessel 

 running above and below the gut, the former being connected with the trunks of com- 

 munication — which course in a parallel manner round the gut — by an intermediate 

 series of inosculating vessels. A fine network is found in the dissepiments and the 

 membranes in connection with the intestinal caeca, as well as certain vessels which 

 end blindly over the dorsal muscles, the nephridia, and other parts. He describes also 

 the growth of the ova in dense masses on the vascular trunks at the bases of the feet. 

 The larger eggs have a fine membranous capsule with nuclei ; the smaller ova are 

 brownish red. 



Grube 3 (1874) says that in large examples of Aphrodita aculeata forty-three seg- 

 ments occur, and that Savigny observes that the two dorsal tufts of hairs (felt) come from 

 the elytra-bearing segments, while Audouin and Milne Edwards held that they come 

 from the cirrus-bearing segments. Grube's examples were in the former condition. 



Cams 4 (1884) mentions that it is called Ti veggo (Claparede) at Naples, a name, 

 however, given to other forms ; and that an Annelid, Branchiomma vigilans, Claparede, is 

 parasitic on it. 



Dr. Hugo Eisig 5 (1887) makes an interesting comparison, with figures, of the 

 bristles and hairs of this species with the golden yellow secretion of the spinning glands 

 of Polyodontes maxillosus. 



1 'Aim. Chset./ Nap., 1868. 



2 ' Niederlandisches Archiv fur Zool./ Bd. i, Heft 2, p. 33, Taf. iii and iv, 1872. 



3 Op. cit., 1874. 



4 < Fauna Medit./ vol. i, p. 199. 



5 ' Monogr. der Capitelliden/ Naples, 1887, p. 331, et seq., Taf. xxxvi. 



