758 J. n. ASinvoHTH. 



distension of tlie vesicles occurs during the breeding season 

 in A. marina, A. grnbii, and A. ecaudata (Gauible and 

 Asliwortli, 1808, pi. iii, iig. 15, and 1900, pi. xxvi, fig. 47). On 

 staining and clearing the nephridia the vesicles are found to 

 still contain either a few large ova or masses of spermatids. 

 The ova are of the same somewhat flattened shape as those of 

 A. assimilis. Their three axes measure 0*195 to 0'20 m.ni, 

 0*16 to 0'175 mm., and 0*075 mm. respectivel}'. (For the 

 measurements of the ova of other species see p. 747.) 



Central Nervous System. — The brain resembles that 

 of the Uschuaia specimens, except that the anterior lobes are 

 much broader. In the specimen 12G mm. long the brain is 

 about 0*7 mui. long, and is broadest across the anterior lobes 

 at the point of origin of the oesophageal connectives. The 

 breadth of the bi'ain at this point is 1*5 mm. and its depth 

 0*4 mm. After the fusion of the two anterior lobes the brain 

 rapidly narrows, so that its middle region is only about 

 0*7 mm. broad. The structure of the anterior lobes is 

 exactly as described for A. assimilis on pp. 748, 749. Near 

 their point of union larger ganglion-cells occnr near the uiiddle 

 linOj gradually iucreasing in unmber posteriori}^ and being found 

 over the whole dorsal face of the neuropile of the mid-brain. 

 In the posterior part of this region there are a few groujis of 

 pyriform, fusiform, or pyramidal ganglion-cells, the stout 

 processes (usually only one to each cell) of which are united 

 into a number of bundles. These processes pass downwards 

 into the ventral portion of the neuropile, where they 

 branch freely (see fig. 23). Similar ganglion-cells extend 

 some distance into the posterior brain lobes. In other 

 respects the brain of these specimens conforms to the 

 description given on pp. 748, 749. 



The oesophageal connectives arise, as usual, from the 

 posterior part of the anterior cerebral lobes. They lie 

 immediately below the epidermis of the metastomial groove, 

 and give off numerous nerves to the skin and buccal muscula- 

 ture. There is a slight swelling on the connective at the 

 origin of the nerve to the otocyst. 



