1919 Agersborg; on Melibe 271 



There are striking similarities between the members of the kladohe- 

 patica, not only between those of any given family^ but also between mem- 

 bers of different families within the section. The former is well illustrated 

 by Tethys and Melibe. This similarity is not only morphological^ but 

 equally true in the manner of living, and in the general behavior as seen in 

 the method of swimming. M, leonina may appear to crawl on the surface 

 of the water with the back downward, or it may float with the back up, the 

 hood having air under it, or the papillae serving as floats. When it has its 

 back down Melibe bends its anterior end alternatingly from side to side to 

 an angle of 45 degrees. These movements are most rapid when the body 

 is relaxed from its bend, making a complete sweep over to the one side, 

 thus pulling the body forward. By this method Melibe moves slowly 

 through the water. Tethys leporina (s. fimbria Linn.) (Bergh, 1877) 

 moves through the water in a similar manner. In this case, however, it 

 is the large veil which plays an important part, together with the right 

 and left bandings of the body. Scyllaea pelagica, classified by Bergh 

 (1871, 1892) in the family scyllaeidae, is described by Collingwood (1879) 

 from the China Sea. Its method of swimming is much like that of Tethys 

 and Melibe. 



Collingwood says in part: "Considerable numbers of this pelagic 

 species were found upon the Sargassum bacciferum floating in Lat. 25 N., 

 Long. 37 W. ; most species of weed having one or more specimens. The 

 animals were in constant movement of contracting and writhing. In the 

 water they swam freely, moving the head and tail from side to side alter- 

 natingly, so as nearly to touch one another ; and when thus swimming were 

 always, owing to the weight of the papillary prolongations and tentacles, 

 back downward, and bore grotesque resemblance to a four-legged animal 

 with long ears, such as a sky terrier." 



Another similarity between Scyllaea and Melibe is their manner of 

 lowering themselves from the surface to deeper water. Scyllaea may be 

 found at the surface or in deeper water. Collingwood mentions it as assum- 

 ing a certain aspect when it falls through the water to a considerable depth, 

 where it is frequently found. Melibe possesses a similar habit. Some of 

 the animals were placed in a large jar of seawater. One morning all save 

 one were apparently dead. All were removed save one, the water changed, 

 and from time to time freshened by oxygenation or renewal. After some 

 days this also seemed dead. It was thought that the water had become 

 stale. Melibe lay absolutely motionless on the bottom, its muscles appar- 

 ently completely relaxed. It showed signs of life only after tlie water 

 had been oxygenated for several minutes. After this the writer became 

 accustomed to this apparent death, and needed only to oxygenate the water 

 to cause the animal to become active again, whereupon it would crawl along 



