382 PROCEEDINGS OF THE ACADEMY OF [May, 



longitudinal muscles; the coronal lobes may be folded into the infun- 

 dibulum, the whole corona and trunk much shortened, and the foot 

 so contracted that its peduncle is brought close to the trunk. 



Hypodermis. — The hypodermis of the trunk is a thin, one-layered 

 epithehum, ^vith relatively few nuclei (Hyp., figs. 20, 22, 23, 25, 27, 28). 

 It bears a hyaline, structureless cuticula (Cut.). On the free margin 

 of the corona it is much thickened and contains large nuclei which are 

 easily seen even in life. In campanulata (PI. XX, figs. 27, 28) this 

 coronal thickening follows the margin of each lobe, and at the tips of 

 the dorsal and ventral lobes are particularly large nuclei. That is 

 also the case with amhigua (PL XIX, fig. 20). In conklini (PI. XX, 

 fig. 25) the dorsal lobe has the hypodermis thickened only at its tip. 

 In coronetta (figs. 22, 23) the hypodermal thickening forms a ring around 

 the base of the lobes, while the hypodermis forming the walls of the 

 lobes is but little thicker than that of the trunk; this is an approach 

 to the condition in Stephanoceros , and wall probably be found to be the 

 case in all forms where the lobes are slender. Another peculiarity 

 of coronetta is that the cuticula covering the lobes is thicker than else- 

 where upon the body ; in the other species I could not distinguish with 

 certainty a cuticula upon the lobes, though probably a deHcate one is 

 present. 



The cilia of the external surface are limited in the adult to the mar- 

 gins and lobes of the corona. In conklini (figs. 25, 26) these cilia are 

 no longer than the corona, and strongly vibratile ; they are found also 

 only upon the tips of the lobes. In coronetta the tip of each coronal 

 lobe bears a tuft of long cilia (fully as long as the trunk), which have 

 a slow undulatory movement; while the sides of the lobes and the 

 interlobular margin of the corona bears much shorter cilia with a more 

 rapid movement. In campanulata (PI. XXI, fig. 37) the ciha fringe 

 the whole free margin of the corona. Here they are longest upon the 

 tips of the lobes, but all have a length greater than that of the corona 

 and trunk together, and sometimes nearly two-thirds that of the entire 

 animal. The cilia in this species are non- vibratile, or at most with 

 slight undulatory movements, and toward their free ends become grad- 

 ually exceedingly tenuous. All preceding authors have figured them 

 much too short, probably because their full length can be determined 

 only with high powers of magnification. These cilia are less hke true 

 cilia than like the tenuous, stiff pseudopodia of Heliozoa; and hke the 

 latter they are extensile and retractile to some degree at least, as is 

 shown by a protoplasmic flowing. They serve not to obtain food par- 

 ticles by ciliary currents, but rather as a wide basket to encompass the 



