296 



SCIENCE 



[Vol. VI., No. 139. 



wMch furnish the luminosity, clearly proves that the 

 presence of a well-defined nervous system is not re- 

 quired for its manifestation, the protoplasm of their 

 bodies alone sufficing for its development. There 

 are no glands for secreting it, and, in some, ap- 

 parently no fatty matter for slow combustion. In 

 the coelenterates the phenomena appear to be more 

 nearly related to nervous manifestations, though in 

 certain cases the luminous matter possesses inherent 

 properties of its own. While in certain annelids, 

 again, such as Chaetopterus and Polycirrus, there are 

 glands which may be charged with the secretion of 

 a luminous substance, it is otherwise with certain 

 Polynoidae, in which the emission of light appears 

 to be an inherent property of the nervous system. 

 The irritability in the phosphorescent examples of 

 the latter family, however, varies considerably, some, 

 e.g., Polynoe scolopendrina, being sluggish, while 

 others, like Harmothoe, are extremely irritable. In 

 the crustaceans the luminosity seems to have the 

 nature of a secretion, probably under the control of 

 the nervous system. In Pyrosoma and Pholas dac- 

 tylus a luminous secretion is also a prominent feature ; 

 and in both the latter and the annelids, decay excites 

 its appearance, as also is the case, to a limited extent, 

 in fishes. 



"It is evident, therefore, that the causation of 

 phosphorescence is complex. In the one group of ani- 

 mals it is due to the production of a substance which 

 can be left behind as a luminous trail. The ease, for 

 instance, with which, in Pennatula and other coe- 

 lenterates, the phosphorescence can be repeatedly pro- 

 duced by friction on a surface having a minute trace 

 of the material, clearly points to other causes than 

 nervous agency. The action, moreover, clearly 

 affects the organic chemical affinities of the tissues 

 engaged. On the other hand, again, as in certain an- 

 nelids, it is purely a nervous action, probably resem- 

 bling that which gives rise to heat." 



Many of the older authors connected the emission 

 of light with the economy of the deep sea : the same 

 notion was brought forward in the ' Report of the 

 cruise of the Porcupine,' 1870; and some naturalists 

 still appear to hold a similar view. After stating the 

 supposed benefits to be derived from the possession of 

 this property by deep-sea forms, Professor Mcintosh 

 suggested that much caution is necessary in theoriz- 

 ing in this direction, explaining that, "In the first 

 place, phosphorescent animals do not appear to be 

 more abundant in the depths of the sea than between 

 tide-marks, or on the surface, the latter, perhaps, pre- 

 senting the maximum development of those exhibit- 

 ing this phenomenon. Very many of the young that 

 have been indicated as so brilliantly luminous be- 

 come surface-forms soon after leaving the Qgg, and 

 thus, at their several stages, more or less affect the 

 three regions, — of surface, midwater, and bottom." 



"A survey of the life-histories of the several phos- 

 phorescent groups affords at present no reliable data 

 for the foundation of a theory as to the functions of 

 luminosity." The irregularity of its occurrence in 

 animals possessing the same structure and habits, 

 the fact that the possessors of phosphorescence 



among annelids are often the inhabitants of tubes, or 

 are commensalistic on star-fishes, in brief, the great 

 variety of condition accompanying its presence in 

 the different groups, necessitates the greatest caution 

 in making deductions, especially if they are to have a 

 wide application. 



THE LEAVES OF THE PITCHER-PLANT. 



The American naturalist for June contains an 

 interesting article by Joseph F. James, upon the evo- 

 lution of the leaves of the pitcher-plant. He con- 

 siders that the ancestral form belonged to the lily 

 family, and that its home was South America, from 

 which, in later times, it spread and modified itself in 

 North America. He supposes that water, lodging 

 on the upper surfaces of some leaves, was retained 

 there; and that in this water insects were caught and 

 drowned. Their decay might have produced a ma- 

 nure which assisted the plant in its growth ; and the 

 plant, finding it advantageous to have a cup-like leaf, 

 would then, in a few generations, have developed just 

 such a leaf as was needed. After a while, boggy land 

 would be found better adapted for its existence, and 

 the pitcher-plant family would be well started. 



The primitive form is now lost; and the most rudi- 

 mentary species is the Venezuelan genus, Heliam- 

 phora (fig. 1), which is simply a hollow tube, with 

 a narrow opening one-fourth the 

 way to the bottom, and with a 

 small rudimentary hood at the 



Fig. 1. Fig. 2. 



top. Nearly the whole interior of the leaf is lined with 

 hairs, those at the bottom long and slender, and those 

 at the top short and thick. They do not seem to be 

 either secreting or absorbing hairs, but serve simply 

 to prevent the escape of insects. The next advance 

 is in our Sarracenia purpurea, so common in the east- 

 ern and northern United States. In this species, there 

 is a more perfect tube, open only at the top, and sur- 

 mounted on one side by an upright hood (fig. 2), the 

 inner surface of which is thickly covered with short, 



