374 PROCEEDINGS OF THE ACADEMY OF [May, 



connection with the walls of the nephridia, particularly with the 

 anterior commissure. 



The immature female. — The free-swimming female (fig. 4), just 

 hatched from the egg, shows the following differences from the adult. 

 The corona is represented simply by a circular hypodermal thickening 

 bearing a row of vibratile cilia; and in the part of the trunk projecting 

 anteriorly beyond this ring lie a pair of large red eyes (£".). The 

 mouth (ilf.) is ventral, and the most anterior portion of the alimentary 

 tract contains short ciUa which do not extend out of the mouth aperture. 

 The cerebral ganglion (Cer.) is much larger than in the adult. The 

 whole hypodermis is thicker, and that portion of it lining the well- 

 demarcated foot (F.) consists of about six huge cells (F.GL) which Gast 

 has shown to be gland cells, by the secretion of which the animal firmly 

 attaches itself. The surface of the foot disk is covered with long ciha. 

 The musculature I have not drawn in this figure, but it is similar to that 

 of the adult. 



STEPHANOCEROS, Ehrb. 



Historical. 



Stephanoceros was discovered in 1761 by Eichhorn, and he later fig- 

 ured it (1775, according to Ehrenberg). 0. F. Miiller (1776) declared 

 it to be a Tubularian, and Oken(1815) also placed it among the hydroids. 

 Goldfuss (1820) first named it, calhng it Coronella fimhriata. Since 

 this generic term was preoccupied Ehrenberg (1832) changed it to 

 Stephanoceros, and called the species Stephanoceros Eichhornii, which 

 all later writers have followed. According to our present generally 

 accepted rules of nomenclature, however, and in justice to Goldfuss, 

 this species must be named S. fimbriatus (Goldfuss) and not S. eich- 

 hornii Ehrenb. Ehrenberg (1832, 1835, 1838) gave good figures of the 

 animal, described the intestine, stomach glands (which all later writers 

 seem to have overlooked), six longitudinal muscles, the ovary, and the 

 flame cells (which he termed gills). Perty (1852) described as a new 

 species *S. glacialis, but this is generally held to be an abnormal indi- 

 vidual of fimbriatus. Leydig (1854) added richly to the knowledge of 

 its anatomy and development. He was the first to note the nucleated 

 hypodermis, circular muscles (he stated there are four longitudinal 

 muscles in the foot which divide dichotomously), the cesophageal tube, 

 ciha in the coronal cup and intestine, lateral canals of the nephridia 

 (with Ehrenberg he regarded these organs as respiratory). Gosse 

 (1855) described minutely the mastax, and in 1862 gave quite a full 

 account of the structure; by experiment he proved the nephridia to be 



