51 



B. Propagation. 



I am inclined to suppose that the Brisinga has two different means of propagation, 

 a sexual and a non sexual process. Such an assumption will not preliminarily appear to 

 be so entirely unreasonable ; since we have (mainly through Liitken •) recently become ac- 

 quainted with some Asteridae in which, collaterally with the usual sexual propagation, we 

 can distinctly demonstrate a multiplication by simple division. A non sexual propagation, 

 somewhat different indeed from this, may I think be claimed for the Brisinga collaterally 

 with the ordinary process. 



a. The sexual propagation. 



As in other star-fishes, only one sort of sexual organs, the ovaries, or the sperma- 

 ries can be developed in the same individual. The sexes are therefore always separate. 

 At the time when the propagation takes place, the ovaries, as well as the testes, swell 

 very considerably; so that the dorsal skin of the arms comes into a state of extremely 

 strong tension. The ripe sexual products issue from the sexual apertures, and are mixed 

 together in the water without any actual copulation taking place. In the captured specimens 

 the sexual products will often be observed issuing from the sexual apertures in the form of 

 a more or less projecting plug, which only little by little is dissolved or becomes diffused 

 in the water. The emission of the sexual products takes place thus as it seems very slowly; 

 and the whole act of propagation extends therefore over a tolerably long period. Only 

 when the specimens have attained their full size, have I found the sexual products mature. 

 In younger specimens, we can indeed always discern both ovaries and testes, but they are 

 still quite solid, with undeveloped contents. In the ovaries there are only found simple clear 

 cells without any deposit of the opaque yellowish red yolk-mass peculiar to the mature 

 ovum; and in the seminaries only the small elliptical bodies whence the characteristic fili- 

 form spermatozoa are subsequently developed. With regard to the time for propagation it 

 appears chiefly to be limited to the summer months. 



b. The non sexual propagation. 



I have certainly not succeeded in ascertaining by direct observation the faculty in 

 the Brisinga of such multiplication by non sexual means; and what I have to state on this 

 subject will be for the present chiefly hypothetical. I feel however bound to produce the 



') Beskrivelser af nogle nye eller mindre bekjendte Slangestjerner, med nogle Bemarkninger om Selvdelingen hos 

 Straaledyrene. (Oversigt over d. Kongl. Danske Vid Selsk. Forliandl. 1872). 



