Arenicola assimilis 131 



The South African examples of the variety affinis afford a striking 

 instance of variation, for nephridia are, without exception, absent in 

 the fourth segment. In examples from other localities, nephridia 

 are invariably present in this segment, and seldom (two out of 

 twenty-four cases) show any marked reduction. 



The oesophageal glands (PI. XIII, Fig. 45) vary in number from 

 six to sixteen pairs, and the number does not appear to be correlated 

 with the size of the worm, for a specimen from Macquarie Island 

 has seven pairs, while another, about half its length, from Susanna 

 Cove, has fifteen pairs. 



PERIOD OF MATURITY, POST-LARVAL STAGES. The writer found 

 that in specimens of A. assimilis var. affinis, taken in Otago Harbour 

 about the end of August, 1902, the nephridial vesicles had been 

 subjected to great distension, doubtless by the accumulation therein 

 of genital products, shortly before capture of the worms. The post- 

 larval example, recorded from Uschuaia by Prof. Ehlers, was found 

 in October, 1892, so that there is a breeding season in that region 

 also about the month of August. 



The mode of deposition of the eggs and the early development 

 are unknown. Only four post-larval specimens (see p. 80), all 

 referable to the variety, have been recorded. Three of these were 

 taken by Mr. E. Vallentin on the surface of the sea near the 

 Falkland Islands, the fourth was found among " roots " of seaweeds 

 at Uschuaia. All were abranchiate. 



DISTRIBUTION. Arenicola assimilis has been recorded from Punta 

 Arenas (Strait of Magellan), Uschuaia (Beagle Channel) and South 

 Georgia. Specimens referable to the variety affinis have been found 

 at the following stations 1 : Uschuaia (an abranchiate post-larva), 

 Lapataia Nueva (Beagle Channel), Susanna Cove (Strait of Magellan) ; 

 the Falkland Islands ; Kerguelen ; Otago Harbour, New Zealand, 

 and islands to the south, namely, Stewart, Campbell, Auckland and 

 Macquarie Islands ; Plimmerton (near Wellington, N.Z.) ; Burnie, on 

 the north coast of Tasmania ; Table Bay and Luderitzbucht, South 

 Africa. 



These records, which show that A. assimilis is a characteristically 



1 It is possible that two examples from Puerto Montt, Chile, recorded on 

 pp. 115, 119 as A. pusilla, may be A. assimilis var. affinis, but, as no evidence 

 of the presence of statocysts could be obtained in these badly preserved speci- 

 mens, they have been placed provisionally in the former species. 



K 2 



