1913.] 



A Study on the Action of Surface Tension. 



537 



a slight amount of lipoid material to which is clue the faint stain given 

 them by scarlet red. In some preparations the spherules appear to take 

 with scarlet red a deeper stain. This is in large measure due to the fact 

 that in the unstained condition they are impregnated with a reddish brown 

 substance absorbed by the tentacles from the cytoplasm of brown Algae 

 (fig. 8). With this brownish material there is associated lipoid material. 

 Hence the deep brownish-red stain which these spherules have after treatment 

 with scarlet red. 



Here and there in the cytoplasm one can detect the presence of fat droplets, 

 which, however, are very minute and few in number. The cytoplasm itself, 

 apart from the spherules, is very finely granular. Especially is this the case 

 in the hillocks from which the tentacles originate. In these hillocks there 

 are no spherules or coarse granules of any kind, and even in the vicinity 

 of, and immediately below, the hillocks, there are very few spherules and 

 large granules. 



The central cavity in which the germinal bud develops is ordinarily very 

 small, but it is enlarged as the bud grows. The wall of the cavity and 

 the surface of the bud are in close contact (fig. 1). The canaliculus which 

 connects this cavity with the exterior is always patent, although in ordinary 

 preparations it may be invisible. 



The nucleus is placed below the germinal cavity and is invisible in the 

 fresh preparation. When a germinal bud is developing the nucleus becomes 

 irregular in shape, a lobate prolongation of it extends into the bud, and 

 this lobate portion is separated by constriction at its narrow part and forms 

 the nucleus of the cell of the developing bud. The process of division is thus 

 amitotic. 



The tentacles are 25 to 40, or even more in number, and they are usually 

 disposed in a radiate direction in all planes from the convex surface of the 

 hillocks. Their diameter is about 1'2-2/j,, and their length, though varying 

 from individual to individual, does not exceed, at the most, 35/z, but 

 ordinarily is not more than 27/j,. The outer end is capitate and its 

 diameter is usually about 2'7/x, that is about half as much again as the 

 average thickness of the tentacles. 



The shaft of each tentacle consists of an axial portion constituted of very 

 finely granular cytoplasm enclosed by an external sheath or layer of homo- 

 geneous material which, because of its slightly greater transparency and 

 refringency, appears readily distinguishable from the axial substance. The 

 thickness of this sheath is about 0'4/j, in the capitate region of the tentacle. 

 The sheath is an extension of the ectosarc, for, at the base of the 

 tentacle, it passes directly into the clear homogeneous limiting layer of 



