SALPA. b 



toiy cavity ; anal orifice terminating close above, and to the right 

 side of, the mouth. Alternately solitary and aggregated. 



The Salpians occur under two distinct conditions, being at one 

 time solitary, and at another associated into circular or lengthened 

 groups. These Salpa-chains vary in length from a few inches to 

 many feet, and swim through the water with a regular serpentine 

 movement, but when taken from the water the individuals of the 

 group are easily detached. Chamisso discovered that the solitary 

 Salpcs do not belong to species distinct from those united in chains, 

 however dissimilar, but are either the parents or the progeny, as 

 the case may be, of the aggregate forms ; and that chained Salpcs 

 do not produce chained Salpcs, but solitary Sa/pce, which in their 

 turn do not produce solitary but chained Salpcs, hence giving rise 

 to the paradoxical statement made in the general observations on 

 the Tunicaries. 



Oenus SAI.PA, Forskal. 1775. 



Animal oblong, sub-cylindrical, truncated in front by the oral 

 orifice, pointed posteriorly ; anal orifice sub-terminal ; test thin, 

 gelatinous, transparent ; muscular mantle in the form of transverse 

 or oblique bands ; mantle cavity lined by a system of vascular si- 

 nuses ; gill rudimentary, forming an oblique band across the inte- 

 rior ; visceral nucleus posterior. Sexes combined. Young produced 

 by gemmation in chains, consisting of individuals unlike the parent 

 and becoming oviparous, the alternate generations only being alike. 



Krolm makes three types, to which all the variations of the asso- 

 ciated Salpcs are reducible. Tlie first is characterized by the ver- 

 tical position of the animals forming the chain, the axes of their 

 bodies crossing the axis of the chain at a right angle. In the sec- 

 ond the bodies of the individuals are more or less inclined to the 

 axis of the chain. The third group is distinguished by the hori- 

 zontal position of the component animals, the axes of their bodies 

 being more or less parallel to the axis of the chain. 



