Miscellaneous. 347 



secretion. Now the chemical products which are phosphorescent 

 at ordinary temperatures are not numerous ; and the one of which 

 one is led to think is phosphuretted hydrogen. It is for the 

 chemists to elucidate this point ; hut, in consequence of the pecu- 

 liarities just indicated, they must not attempt to ascertain its pre- 

 sence directly, hut rather to see whether there are, in the cellular 

 protoplasm of the apparatus, the materials necessary for the produc- 

 tion of this gas. 



What inclines me in favour of this hypothesis is the extreme 

 resemblance that we observe between the phosphorescence of sub- 

 stances in decomposition, which is due to an evolution of phos- 

 phuretted hydrogen, and that of luminous animals. They present 

 the same physical characters, the same affinity for oxygen, and 

 only differ in this particular, that the cadaveric phosphorescence is 

 continuous, like the decomposition of the substances which produce 

 it, whilst the phosphorescence of the animals is intermittent. The 

 latter is due to the fact that the cellular decomposition which sets 

 free the luminous product, takes place in animals of high organi- 

 zation only under excitation of the nervous system, and in the lower 

 animals (Noctilucce) only by means of external excitants. 



My investigations upon the glowworm and the experiments that 

 I have made upon the Noctilucce lead me to regard phosphorescence 

 as a general property of protoplasm, consisting in an evolution of 

 phosphuretted hydrogen. This mode of looking at it easily explains 

 how many of the lower animals, although destitute of a nervous sys- 

 tem, are phosphorescent. Further it presents the advantage of en- 

 abling us to connect the phenomena of phosphorescence observed in 

 living creatures with those which are observed in organic matters in 

 course of decomposition. It is another example of a biological 

 phenomenon very clearly reduced to an exclusively chemical cause. 

 — Comptes Bendus, February 16, 1880, p. 318. 



On the French Jurassic Cidaridse. 

 By M. G. Cotteatj. 



M. Cotteau, having completed the revision of the Jurassic Cida- 

 ridoe in the ' Paleontologio Franchise,' has communicated to the 

 Geological Society of France an interesting summary of his results. 

 Of French fossil urchins he refers to this family 121 species, of 

 which 87 belong to the old genus Cidaris, 25 to lihahdocidaris, and 

 9 to Diplocidaris. The 121 species all belong to tho Jurassic 

 epoch : none of them existed before it ; and none occur in the Creta- 

 ceous deposits. Most of them are also limited to a single stage 

 of the Jurassic. 



The Bhastic stage contains a single peculiar species. The Sine- 

 murian (Infra -Lias) has 7 peculiar species, mostly represented by 

 detached spines. The Liassic stage possesses 10 species, 9 of which 

 are confined to it, while the tenth extends up into tho next stage, 

 the Toarcian (Upper Lias shale), which, however, contains only 3 

 species in all. Tho species just referred to (Ehabdocidaris horrida) 

 also passes into the Bajoeian (Inferior Oolite) stage, in which the 



