398 M. E. Grube on the Capitellse 



Iceland. But the distribution of Capitella capitata is not closed 

 with the Icelandic and English coasts ; for the Lumbricus cana- 

 lium, mentioned en passant by Nardo as an inhabitant of some 

 of the shallower and less frequented canals of Venice*, is like- 

 wise nothing but our Capitella, as I have ascertained by the 

 examination of the spirit specimens captured by him. Whether 

 it. also occurs on the French coast has not yet been ascertained. 



The determination of the position which the genus Capitella 

 should occupy in the system appears to Claparede not to be 

 settled by the discussion with which Van Beneden closes his 

 memoir ; and I am of the same opinion. Van Beneden comes 

 to the conclusion that the Capitella, are dioecious Lumbricinse : 

 all that can be cited in favour of the supposition that they be- 

 long to the Polychsetae is limited to the mode of development, to 

 the form of the embryos, which escape into the world with a 

 globular body, with two eyes and two tufts of cilia close to these, 

 and then pass through a metamorphosis, a posterior circlet of 

 cilia being added to the ciliary circlet before the eyes, which 

 originates in the above-mentioned tufts, and the portion of the 

 body between these extending itself and dividing into rings ; 

 the absence of vessels and the distribution of the male and 

 female sexual organs upon two individuals are not of sufficient 

 importance to have much stress laid upon them. But what is 

 there positively in favour of referring the Capitellce to the Lum- 

 bricinse, and in what signification is this name taken ? It does 

 not correspond with the family which I have established under 

 this name, as Van Beneden also refers to it Tubifex (Scenuris), 

 Enchytrceus, and Chcetogaster, but rather to D'Udekenr's sub- 

 order of Agemmes, which forms the opposite to his Gemmipares 

 (the Na'ides). As the Lumbricinas, in D'Udekem's sense, in- 

 clude nothing but Annelides with series of but slightly project- 

 ing uncini standing singly or in pairs, Capitella would approxi- 

 mate to them less than to Tubifex, a genus three of the six spe- 

 cies of which occur in the sea ; whilst for the Lumbrici the pro- 

 portion of marine forms is far less favourable. 



The organization of the Agemmes is expressed (besides the 

 occurrence of vmcini, rarely also of setre) especially in the con- 

 centration of the genital organs in certain limited regions of the 

 body, in their hermaphrodism, and in the appearance of the so- 

 called loop-like organ ; whilst external organs of respiration never 

 appear (except in Alma nilotica). If, therefore, the Capitellce be, 

 as Van Beneden supposes, Lumbrici of a low degree of organiza- 

 tion, this degeneration of the type shows itself in the disap- 

 pearance of the blood-vessels and the simpler arrangement of 



* Prospetto della Fauna marina volgare del Veneto estuario, 1847, p. 11. 



