564 



NA TURE 



{Oct. 5, 1882 



being flat for adherence to rocks is closed in so as to hold a 

 small mass of air. Suspended by the buoy so formed, they float 

 at the surface mouth downwards. The one of which a figure 

 is now on the screen Minyas arrulea, is remarable as being one 

 of the small band of Pelagic animals which is coloured deep 

 blue. There are also Pelagic insects of the genus Halobates of 

 the Bug family, and closely allied to the common water bugs 

 which skip on the surfaces of our ponds. Halobates is found 

 clinging to the surface of the waves at all distances from land in 

 the open oceans, and outrides the heaviest storms. 



There are many Pelagic fishes ; I have already shown you 

 the dolphin (Coryphxna). Here is a figure of one of the 

 Ribbon Fishes, the scarce Regalecus. This fish has usually 

 been supposed to be a pelagic fish, but Dr. Gunther is per- 

 suaded that it is a true deep-sea fi%h, though it has not yet 

 been caught in any deep-sea net, only picked up dead en the 

 surface. There are many similar fishes about which some 

 difference of opinion as yet exists as to their habits. The 

 young of the Ribbon Fishes are found alive at the sea surface, 

 and the group may therefore perhaps yield another instance of 

 the connection of Pelagic with deep-sea forms. The Pelagic 

 snakes are interesting as, to some extent, modern representatives 

 of the Eocene sea serpents (Titanophis), for though they come on 

 shore to produce their young, their existence is mostly spent at 

 the sea surface often far from land, and they are specially 

 modified both in the structure of their lungs, and the ribbon- 

 like flattening of their tails for pelagic existence. 



There is one lizard, the well known Amblyrhynchus of the 

 Galapagos Islands, described by Mr. Darwin in his Journal, 

 which though it cannot in any way be termed pelagic swims out 

 to sea, and as the only recent one which does so is worth mention 

 as a sort of representative of the gigantic pelagic lizards of 

 Mesozoic periods such as Mososaurus. 



With so many groups of the animal kingdom contributing to 

 the Pelagic fauna, it is remarkable that some large groups should 

 be entirely unrepresented within it. There are no adult Pelagic 

 sponges, no Alcyonarians, no Sipunculids, no Brachiopods, no 

 Lamellibranchs, and lastly no Echinoderms. Considering the 

 curious adaptations to Pelagic life which have been undergone 

 by such forms as sea anemonies, nemertines, compound a-cidians 

 and gasteropods, it is mo-t easy to conceive how- Lamellibranchs 

 for example taking after the habit of flying as it were butterfly 

 fashion thrc ugh the water like Luna hyans, might have become 

 Pelagic, and how Echini taking after Minyas, or Comatulae 

 swimming with their arms or Holothurians in various ways might 

 have assumed a Pelagic dress, but no Lamellibranch, and no 

 Echinoderm seems ever in the long record of the past to have 

 been Pelagic since the time of their earliest Pelagic ancestors, 

 unless possibly Saccoma of the lithographic state was Pelagic. 



With regard to the history of the Pelagic fauna in the past. 

 There can be no doubt, as Prof. Weissmann so well puts it, 

 that "the birth place of all animal and plant life lay in the sea." 

 It is probable that a considerable part of earliest life which 

 existed must have been Pelagic, and that the ancient Pelagic 

 fauna was to a large extent the parent cf all other life. The 

 developmental history of all marine animals points clearly in this 

 direction, closely similar transparent Pelagic larval forms being 

 common to groups of widely different adult littoral forms. The 

 resemblance between the larvae of these adult forms can hardly 

 be conceived to have been arrived at by natural selection after 

 the adult forms had already diverged from one another. It is 

 only to be explained on the hypothesis of an original Pelagic 

 ancestral condition. One of tire Monera, Protomyxa aurantiaca, 

 is even now a Pelagic form, having been found by Prof. Haeckel 

 adhering to a floating spirula shell. 



From the recent interesting researches of Dr. Nathorst, 1 we 

 know that Scyphomedusae closely like those now swimming in 

 Southampton Water, were already among>t the Pelagic fauna of 

 the Cambrian Sea, whilst the mud at the same time swarmed 

 a ith annelids very similar to those now existing. At the same 

 remote epoch Brachiopods, Corals, Echinoderms, Crustacea, 

 and other forms were already present on the coasts. 



The Precambrian Pelagic fauna must therefore probably have 

 contained sexually ma' r.re representatives of the Planula, the 

 Bilateral Echinoderm la va, the Ephyra (which survives as such 

 to the present day), the Trochosphere and the Nauphus. During 

 the Cambrian period or e irlier, was added the Cypris ancestor of 

 Cirripeds, and the vertel ra.te ancestor, and the Trilobite ^Eglina 

 with gigantic eyes found its place in the dim light somewhere, 

 ' Svenska Vetensk. Akad. Hand., No. 7. Bd. xviii. 



possibly amongst the Pelagic fauna. In Silurian times Ptero- 

 pods were added to the Pelagic throng, some gigantic forms of 

 w Inch nearly a foot in length are now extinct, whilst one genus 

 then present still flourishes in modern seas, the Heteropods also 

 appeared (Bellerophon) and Cirriped larvae, and the Graptoliths, 

 possibly Pelagic, appeared and became extinct. In the Devonian 

 period certain sharks and rays and ganoid fishes probably took 

 to Pelagic life. Pelagic representatives of the sharks and rays 

 still flourish, but the ganoids have retreated to the fresh water-. 

 In the early Secondary period Globigerina appeared and a few 

 Radiolarians, and the dibranchiate cephalopods came into being 

 and soon the sea swarmed with the Pelagic Belemnites. The 

 air-breathing reptiles whose ancestors had quitted sea life and 

 gone on shore came back to Pelagic life and the Ichthyosaurus 

 w ith enormous eyes chased the Pelagic prey in the depths, or 

 hunted at night. Somewhat later the ancestors of the Moso- 

 saurids took to the sea ; and their progeny became entirely Pelagic 

 and as huge as whales. 



In early tertiary times, or shortly before that, various mammalia 

 took to the sea, and amongst them the whales became entirely 

 pelagic and relinquished the shore allogether. Some animals 

 have apparently taken to oceanic life, in very recent times 

 indeed. Ianthina is an instance in point, it has not as yet been 

 discovered in the fossil condition at all, nor any close allies 

 of it. 



Somewhat thus has the Pelagic fauna grown up, having been 

 partly composed of animals : the ancestry of which has probably 

 led a Pelagic life from the earliest times, and partly added to, at 

 all ages by inhabitants of the coast, and the dry land which 

 have as it were from time to time run away to sea. 



In conclusion, I can only say that it has given me the greatest 

 pleasure to address a lecture to you on the present subject in a 

 city, the population of which is itself so largely Pelagic. It is 

 to a considerable extent through the careful collecting of the 

 Captains of merchant vessels interested in zoology on the high 

 seas, who have gathered specimens for the Museums of their 

 home ports, that many of the facts I have laid before you to- 

 night have been brought to light, and all praise is due to thtm 

 for the fact. 



UNDERGROUND TEMPERATURE 



T'HE Underground Temperature Committee of the British 

 -*• Association have presented a summary (drawn up by Prof. 

 Everett) of the results contained in all their reports (fifteen in 

 number) up to the present date, of which the following is an 

 abridgment : — 



The results are classified under the heads : A. Instruments. 

 B. Methods of observation. C. Questions affecting correctness 

 of observations. D. Questions affecting deductions from ob- 

 servations. E. Comparison of results. F. Mean rate of 

 increase of temperature with depth, and mean upward flow of 

 heat. 



A. Instruments. — Under this head we have : I, Instru- 

 ments for observing temperature. 2. Subsidiary apparatus. 



1. The thermometers which the Committee have employed 

 have been of two kinds — slow-action thermometers and maxi- 

 mum thermometers. The present pattern of slow-action ther- 

 mometer consists of a thermometer having its bulb surrounded 

 by stearine or tallow, the whole instrument being hermetically 

 sealed within a glass jacket, and had its origin in ,a conference 

 between the secretary and Dr. Stapff in the St. Gothard 

 Tunnel. 



Cur present patterns of maximum thermometer are two — the 

 Phillips, and the Inverted Negretti— both being hermetically 

 sealed in strong glass jackets to prevent the bulbs from receiving 

 pressure when lowered to a great depth in water. 



Both instruments are used in a vertical position, and they 

 register truly in spite of jolts in hauling up. 



References to Becquerel's thermo-electric method of observing 

 underground temperature were made in three of the reports, and 

 some laboratory experiments were subsequently carried out by 

 the secretary, which led to the conclusion that the method could 

 not be relied on to yield sufficiently accurate results. It may be 

 mentioned that Becquerel's observations are only carried to the 

 depth of 100 feet, whereas we require observations at the depth 

 of 1000 or 2000 feet. 



2. Under the head of subsidiary (that is non-thermometric) 



