STUDIES IN SPICULE FORMATION. 45 



Studies in Spicule Formation. 



VI. — The Scleroblastic Development of the Spicules in some 

 MoUusca and in one Genus of Colonial Ascidians. 



By 



%V. Woodland, 



Demonstrator of Zoology, King's College, Loudon. 



Witii Plate 5. 



Spicules in Nudibranch Mollusca. 



The imdibranchs examined^ all obtained from Plymouth, 

 consisted of three genera — Goniodoris castanea^ Archi- 

 doris tuberculata, and Lamellidoris bilamellata. 

 Most of my specimens were simply fixed and preserved in 

 absolute alcohol, and were, in consequence, much contracted; 

 others were fixed with 1 per cent, osmic acid, opened to give 

 admission to the stain, and stained as usual with picro-cai-mine 

 (three hours), and I received them in this condition. In both 

 cases I divided the animals horizontally into halves (with 

 scissors), and in each instance scraped away Avith a scalpel 

 the viscera and most of the musculature of the body-wall, 

 until the portion of integument left looked to some extent 

 translucent (whether unstained or stained). I usually found 

 that the integument of the foot showed the spicules better 

 than that of the dorsum. The unstained portions of integu- 

 ment (alcohol specimens) I stained in a saturated solution of 



