1903.] NATURAL SCIENCES OF PHILADELPHIA. 375 



excretory and not respiratory, found the contractile vesicle, four flame 

 cells on each side of the body, described the dorsal glandular mass 

 (found by Leydig) as the brain, and described five pairs of longitudinal 

 nmscles. Cubitt (1870) found the lateral sense-organs, but made the 

 serious error of supposing that each of them was connected with a 

 flame cell (his pulsatile sac), and supposed them to be respiratory 

 structures for taking water into the nephridial tubules; he carefully 

 described the ciliary wreath within the coronal cup, but mistook (Uke 

 Leydig and most of the later describers) the dorsal glandular body for 

 the brain. Hudson and Gosse (1886) gave very good figures ; found five 

 flame cells on each side of the body, described the connection of the lateral 

 canals with the contractile vacuole, discovered the dorsal sense-organ, 

 and described six pairs of longitudinal muscles. Vallentin studied 

 stained sections; he found that large hypodermal cells of the foot 

 secrete the tube ; that the dorsal mass is not nervous but glandular and 

 opens by a duct into the vestibule; he regarded the large hypodermal 

 cells at the bases of the arms to be nerve cells. The male of this species 

 has been described by Western (1893) and more carefully by Dixon- 

 Nuttall (1896). Less important are the papers of Dujardin (1841), 

 Weisse (1845), Dobie (1854), Pritchard (1861), Cubitt (1869), Peirce 

 (1875), Rosseter (1881, 1884), Lord (1885), Jennings (1894, 1896, 1900, 

 allfaunistic). 



Anato:mical. 



Nothing new can be added to our knowledge of the external jorm 

 (PL XIX, fig. 16). The margin of the corona is prolonged into five 

 long arms, which are slightly fiattened and extensile. These arms are 

 shghtly curved, and the dorsal, unpaired one slightly longer than the 

 others. The body is long and slender, rather strongly demarcated 

 from the long foot which ends in a short peduncle (fig. 14). The gela- 

 tinous tube (Tub.) is very transparent, with annular folds, elastic and 

 of great thickness. 



Hypodermis. — The hypodermis {Hyp., figs. 9-11) of the trunk is a 

 thin layer with flattened nuclei. At the margin of the corona it is 

 much thickened, so as to form at the base of each of the arms a mass of 

 four or five large rounded nucleated cells. The hypodermis of the arms 

 is about as thick as that of the trunk, but neither in the living state nor 

 upon preparations in which the nuclei of other regions of the hypoder- 

 mis are stained very sharply are nuclei to be found in it. The hypo- 

 dermis of the arms of the corona would therefore appear to be a direct 

 continuation of the cytoplasm of the large hypodermal cells at the 



