DESCRIPTIONS OF GENERA AND SPECIES 181 



such as is found in the Enchytraeidae. The colour of the blood -plasma of 

 A. hemprichii is stated by Lankester (6) to be of a pinkish colour. 



The nervous system consists of little else than the cerebral ganglion. The simplest 

 cerebral ganglia are those of A. variegatum, where the fissure indicating its double 

 nature is hardly visible ; in A. tenebraruni it is most complicated, with well-marked 

 lateral lobes ; this species also alone shows any traces of a ventral nerve-cord, which 

 is very short and is not connected with the brain. The latter is perfectly continuous 

 with the epidermis, and is composed of cells dorsally and of nerve-fibres ventrally 

 (A. variegatum) or of cells only ; it gives off numerous branches. Vejdovskt 

 throws considerable doubt upon Maggt's description of a ventral cord in A. hemprichii, 

 which is not accompanied by any figures. 



Generative organs. The generative organs of Aeolosoma .have been described by 

 d'Udekem (2), Maggi, and more recently, as well as more fully, by Stolc (1). 

 The reproductive organs are only occasionally developed, the usual mode of repro- 

 duction being by budding and division. Curiously enough, sexual and asexual 

 reproduction may be, according to d'Udekem (2) carried on pari passu. Maggi's 

 figure of the ovaries and oviducal pores (fig. 8) is, it should be observed, an 

 almost exact copy of that of d'Udekem (2, fig. i) ; in another figure, however, he sup- 

 plements d'Udekem by illustrating the spermathecae, which were apparently not seen 

 by d'Udekem. All these observers appear to have investigated the same species, viz. 

 A. hemprichii and A. quaternarium. The testis is median and unpaired, and lies in 

 the fifth segment ; the ovary occupies a corresponding position in the sixth segment. 

 As has been already mentioned, there are no sperm-ducts, the nephridia, particularly 

 that of the sixth segment, which is slightly different in structure from the rest, 

 serving as conduits of the sperm. The ova, which are few and large, and apparently 

 undergo amoeboid movements, escape by a large pore on the ventral surface of the 

 sixth segment. The spermathecae are small oval sacs, one to three pairs occupying 

 segments iii-v. 



At the epoch of sexual maturity a clitellum is formed, which is figured by Stolc 

 as limited to segments v-vii; it is only developed on the ventral side of the 

 body. It is not known whether a cocoon is formed ; the structures described by 

 Eheenberg, and described and figured as developing eggs by Maggi, are probably, 

 as Vejdovsky (24) suggested, encysted worms. At any rate, I have recently been 

 able to show (27) that this annelid can encyst itself. The cysts are of variable 

 thickness, usually spherical, but sometimes oval or of irregular form. I found them 

 at the commencement of cold weather, at the end of autumn. 



The asexual propagation of Aeolosoma has been studied by Vejdovsky; the 



