52 



BRITISH TUNICATA. 



The mantle of this species (PL XXV, figs. 2 and 3) 

 is very delicate and transparent ; but the radiating 1 

 muscles at the base of the tubes are well developed. 

 The branchial folds (fig. 40) are rather narrow and 





: 



FIG. 40. Part of branchial sac of Molgula simplex. Much enlarged. 



have on each side two or three membranous bars or 

 rods and one immediately at the base. The spirals are 

 large and distinct, though without perfect regularity ; 

 there appears to be but one to each branchial pouch ; 

 the meshes are wide and irregular in size and form ; 



FIG. 41. A tentacle of Molgula simplex. Highly magnified. 



the radiating vessels are distinct and pretty-regularly 

 arranged. The branches of the tentacular filaments 

 (fig. 41) are rather irregularly disposed so as to give 

 them a bushy appearance. The extremity of the lower 



