48 DR. M'INTOSH on BRITISH SALP^. 



minous in the twilight in the sea, neither were the two forms of 

 S. spinosa ; but when the latter were enclosed in a bottle, bright- 

 greenish phosphorescent sparks were emitted on jarring the vessel 

 in the dark ; this, however, may have been due to the presence of 

 other minute oceanic forms. There was no luminous appearance 

 when the vessel was left quiescent in the dark ; and none of the 

 forms of either species were observed to give out the bright- 

 greenish phosphorescence that invariably gilded the luminous 

 Medusae and Annelids for a few seconds after immersion in spirit. 

 A curious appearance was caused on the beach, during the ple- 

 nitude of Salpa life, by the occurrence of two days of iine weather. 

 The dried bodies of the beached Salpae left whitish, glistening, 

 scale-like patches on the black gneiss-stones and bare rocks near 

 high-water mark ; and when the chains of 8. spinosa happened to 

 subside without separation, an appearance was produced like the 

 frond of Asplenium viride or TricJiomanes, or the fossil imprint of 

 some primeval fern, 



DESCEIPTION OF PLATE I. 

 [Figs. 1, 2, 3, 6, 7 and 8 are from carefully made spirit preparations.] 



Fig. 1. Salpa runcinata, with young solitary form (true embryo of Huxley) 

 in its interior. Enlarged, a, the embryo ; b, the nucleus of the 

 adult ; c, the branchise ; d, the endostyle. 



Fig. 2. An adult solitary form of the same species, about the natural size. 

 a, nucleus ; 5, peculiar network of vessels ; c, branchise ; f, de- 

 veloping chain of young ; h, endostyle. 



Fig. 3. A lateral view of another, smaller solitary form, showing the embry- 

 onic body at a, and the network of vessels at b. Enlarged. 



Fig. 4. A very young soHtary form of S. runcinata. a, large embryonic 

 body ; h, nucleus ; c, intestine. The muscular bands, brancliise, and 

 endostyle are apparent. 



Fig. 5. Salpa spinosa, enlarged, from a Uving specimen, a, ocellus ; b, four 

 minute opake dots ; e, branchise ; d, nucleus ; e, inner tunic with 

 its muscular bands ; /, coiled chain of young ; g, bifid spinous pro- 

 cess ; h, endostyle. 



Fig. 6. A lateral view of one of the same species, enlarged. 



Fig. 7. Young soHtary form of Salpa spinosa (?), enlarged, a, embryonic 

 body ; 6, bifid spinous process ; c, trumpet-shaped ending of 

 inner tunic (mantle) in the posterior spine ; rf, nucleus. 



Fig. 8. A lateral view of the same specimen. The letters are similarly 

 placed. 



Fig, 9. The aggregate form of S, spinosa, enlarged, from a somewhat con- 

 tracted living specimen, a, bluish-piu-ple nucleus ; c, branchise ; 

 h, endostyle. 



