720 on the spawn and young op a poltoh etb worm. [Dec. 17. 



whatever it be, which makes it undesirable i'or so many other 

 Eunicid lame to pass through a pelagic stage, is at work here 

 also ; only that, instead of the early development being accom- 

 plished in the spawn-jelly, as in group ii., or in the body-cavity 

 of the mother, as in Marphysa sanguined, the larvoo make use of 

 the power, which they share with those of various other Poly- 

 chsetes, of secreting mucus in quantities from their epidermal 

 glands, to attain the same end of providing a fixed resting-place 

 during the formation of the more important organs of the body. 



BIBLIOGRAPHY. 



(1) Claparede (E.) und E. Metsciixikoit. — " Beitrage zur 



Kenntnis der Entwicklungsgesehiehte der Polvchiiten." 

 Zeit. f. wiss. Zool. xix. (1S69). 



(2) Fewkes (J. W.). — " On the Development of certain Worm- 



Larvse.'' Bull. Mus. Comp. Zool. Harvard, xi. (1885). 



(3) Haecker (V.). — " Pelagische Polychiitenlarven." Zeit. f. 



wiss. Zool. lxii. (1^97). 



(4) Kocn (H.). — " Einige Worte zurEntwickelungsgeschichte von 



Eunice/' Neue Denkschr. Allg. schweiz. Ges. Naturw. 

 viii. (1846). 



(5) Krohn(A.)uikI A. Schneider. — " Ueber Annelidlarven mit 



poriisen Hiillen."' Arch.f. Auat. 1867. 



(6) MI'ller (J.). — "Ueber die Jugendzustiinde einigerSeethiere." 



Monatsber. Akad. Berlin, 1851. 



(7) Salenskt (AY.). — "Etudes sur le developpement des Anne- 



lides," deuxieme partie. Arch. Biol. vi. (1887). 



(8) Webster (H. E.). — "On the Annelida Chastopoda of the 



Virginian Coast." Trans. Albany Inst. ix. (1879). 



(9) Wilson (E. B.). — "Preliminary Abstract of Observations 



upon the Earlv Stages of some Polycha?tous Anuelides.'' 

 Zool. Anz. hi. (1880). 

 (10) Wilson (E. B.). — " Observations on the Early Developmental 

 Stages of some Polychaetous Annelides." Stud. Biol. Lab. 

 .Job. Hopk. Univ. ii. (1882). 



EXPLANATION OF PLATE XXXIX. 



Spawn and young of a Polyclwte Worm of tbe genus Ma/rphysa, 

 Fig. 1. Spawn-mass, unbroken, somewhat reduced, p. 715. 



2. Spawn-mass, broken, showing embrvoi-' and pellicle, somewhat 



reduced, p. 715. 

 .'!. Embryo in striated coat, greatly enlarged. The outline of the 



ectoderm underlying the coat is not shown, p. 710. 

 t. Young, stage 2, greatly enlarged, p. 716. 



p. 71 r>. 

 p. 717. 

 „ P- 717. 

 p. 717. 

 p. 718. 

 „ p. 718. 

 10«. Jaws of stage 11, more highly magnified, p. 719. 

 in/*. Setae „ „ „ p. 719. 



The figures, which are copies of working drawings of the living objects, are 

 not drawn to scale; but nos. 4-10 are very roughly so. 



0. 



6. 



» 6, 

 ., 4, 



7. 



„ 6. 



s. 



., 7, 



9. ,[ 



,, 8, 



10. 



„ 11, 



