764 MICROSCOPIC FORMS OF ANIMAL LIFE 



Professor James -Clark (U.S.A.), 1 followed by those of Stein, Saville 

 Kent, 2 and Bergh. In some of these a sort of collar-like extension of 

 what appeal's to be the protoplasmic ectosarc proceeds from the anterior 

 extremity of the body (fig. 585, cl), forming a kind of funnel, from the 

 bottom of which the nagellum arises ; and by its vibrations a cur- 

 rent is produced within the funnel, which brings down food-particles 

 to the 'oral disc ' that surrounds its origin while the ectosarc seems 

 softer than that which envelops the rest of the body. Towards the 

 base of the collar a nucleus (n) is seen ; while near the posterior 

 termination of the body is a single or double contractile vesicle (cr). 

 The body is attached by a pedicel proceeding from its posterior 

 extremity, which also seems to be a prolongation of the ectosave. 

 These animalcules multiply by longitudinal fission ; and this, in 

 some cases (as in the genus Monosiga), proceeds to the extent of a 

 complete separation of the two bodies, which henceforth, as in the 



ordinary Monad //<". 

 live quite independ- 

 ently of each other. 

 But in other forms, as 

 Codosiya, the fission 

 does not extend throng] i 

 the pedicel, and the 

 twin bodies being thus 

 held together at their 

 bases, and themselves 

 undergoing duplicative 

 fission, clusters are pro- 

 duced which spring 

 from common pedicels 

 (fig. 586) ; and by 

 the extension of the 

 division down tin- 

 pedicels themselves, 

 composite arborescent 

 fabrics, like those of 



FIG. 585. Single zooid of Codosiga umbellate : cl, ^x^l^+oc -IVP nvn 

 collar ; n, nucleus ; CD, double contractile vesicle. ><>pliytes, aie P 1( 



duced. 



In another group a structureless and very transparent horny 

 calyx, closely resembling in miniature the polype-cell of a Campanu- 

 laria, forms itself round the body of the monad, which can retract 

 itself into the bottom of it ; and in the genus Salpingonca both 

 calyx and collar are present. In some forms of this group multi- 

 plication seems to take place, not by fission, but by gemmation ; 

 and, as among hydroid polypes, the gemma* may either detach 

 themselves and live independently, or may remain in connection 

 with their parent-stocks, forming composite fabrics, in some of which 

 the calyces follow one another in linear series, while in others they 



1 See his memoirs in Ann. Nat. Hist. ser. 3, vol. xviii. 186(5; oj). cit. ser. 4, vol. i. 

 1868 ; vol. vii. 1871 ; and vol. ix. 1872. 



2 See his Manual of tin; Itifnnuria, 1880-82, 2 vols. and 1 vol. of plates. 



