SOLMISSUS MAESHALLI. 65 



which the tentacles arise seems to form the extreme margin. Seen from be- 

 low (PI. 16, fig. 5) the lappet region and velum entirely conceal the gastric 

 pockets. The lappets are about as broad as long, square, with the margin 

 hardly if at all incised in the radii of the peroniae. The number of tentacles 

 is variable, the maximum number observed being sixteen. The specimen de- 

 scribed by Agassiz and Mayer had fourteen, a number found in one of the 

 present specimens also. The smallest number observed was eight ; this, 

 strangely enough, was in a moderate-sized individual, 28 mm. in diameter, 

 (PI. 16, fig. 6), and it appears to be the adult number in this specimen, since 

 there is no trace of any further development of tentacles. Rudimentary 

 tentacles are, however, present in small specimens. It is interesting to note 

 that in the development of new tentacles the new peroniae appear first, and 

 then the tentacles ; in one specimen such a peronia is visible while the ten- 

 tacle has not commenced to grow. In no case was a developing tentacle 

 observed in a large specimen. It appears, then, that the full number of 

 tentacles, though not very early developed, is attained long before the 

 medusa attains its full size and sexual maturity. The tentacles are carried 

 radiating stiffly outward from the bell in life. 



The number of otocysts per lappet is variable, and appears to increase con- 

 stantly with the growth of the medusa. The largest number observed in any 

 one lappet was fifteen, in the case of the largest specimen, but it is doubtful 

 whether this is the maximum. This is about twice as many as are known 

 to occur in S. albescens, the greatest number recorded for one lappet of that 

 species, so far as I can learn, being seven. In small specimens the number 

 of otocysts per lappet is much smaller. Thus, in the smallest specimen, 

 13 mm. in diameter, there are two, three, three, and in one very narrow 

 lappet, evidently recently formed by the development of a new peronia and 

 tentacle, only one. In medium sized individuals there are usually from seven 

 to ten per lappet. Agassiz and Mayer (: 02) were able to find only one 

 otocyst, on account of the poor condition of their specimen. 



The sense organs themselves so closely resemble the condition described 

 and figured by the Hertwigs ('78) for S. albescens that no detailed account 

 is necessary here. The sensory pad supporting the sense organ is large and 

 some at least of the spindle-shaped ectoderm cells bear bristles (PI. 21, 

 figs. ^, 8). The otocyst is small in comparison with the pad, and contains 

 a single otolith, which is not crystalline but rounded, even in fresh specimens. 

 There are no otoporpae. 



