and Illustrations i?i Natural History, 259 



object, but are completely at a loss to account for the manner 

 in which it is brought about ; for these animals have nothing 

 analogous to teats, the embryos have no visible attachment to 

 the mother, appear to be in no capacity to take food, nor to 

 carry on the respiratory function. It is, nevertheless, pro- 

 bable, that the secretion in which they are immersed consti- 

 tutes the source of their nutrition, whether taken in by suction 

 or by absorption ; yet, if we admit this, what are we to think 

 of the function of respiration, thought to be equally neces- 

 sary with nutrition to the continuance of life and the evolu- 

 tion of the foetus, as the subgelatinous secretion appears to 

 exclude the direct influence of the ocean upon the respiratory 

 organ, which, moreover, does not appear to be developed 

 until the moment prior to their exclusion from the pouch. 

 This circumstance, taken in conjunction with the suspicions 

 of some physiologists as to the oxygenation of the foetal 

 blood, may lead to such further observations as may tend 

 to throw some new light upon this still obscure function in 

 the foetus." (p. 18, 19.) The author, in this comparison, 

 may seem to have forgot that the opossum is a viviparous 

 animal, while his shrimp is oviparous. But this is an error 

 on the part of the reader; for, in an appendix to the memoir 

 contained in No. ii., he tells us, that, when he speaks of 

 the gradual deveiopement of the embryo of the shrimp, it 

 is not the egg of which he speaks, but the embryo divested 

 of the tunics which envelope the ovum on its first exclusion. 

 In the other Crustacea with a pouch analogous to that of the 

 Mysis, it serves merely as a protection to the eggs, which 

 hatch all at once, and exclude the young in a perfect state, 

 as we see in most oviparous animals. 



The third memoir is occupied with the discussion of one of 

 the most remarkable phenomena in nature, the luminosity of 

 the ocean ; but as there has already appeared in our journal 

 an able paper on the subject by Mr. Baird, w^e will confine 

 ourselves at present within narrow limits. There are five 

 principal varieties of luminosity (we adopt our author's word, 

 although it is an awkward one) : the first shows itself in scat- 

 tered sparkles in the spray of the sea, and in the foam created 

 by the way of the ship, when the water is slightly agitated by 

 the winds or currents ; the second is a flash of a pale light, of 

 momentary duration, but often intense enough to illuminate 

 the water to an extent of several feet; the third, of rare 

 occurrence, and peculiar to gulfs, bays, and shallows, in warm 

 climates, is a diffused pale phosphorescence, resembling some- 

 times a sea of milk, or of some metal in a state of igneous 

 liquefaction; the fourth presents itself to the astonished 



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