December 30, 1915] 



NATURE 



493 



both sight and hearing would be less acute in the 

 fatigued person ; and the fact that such is not always 

 the case tells rather against the value of the tests as an 

 index of fatigue. Taking into account, however, the 

 comparatively small number of observations recorded 

 up to the present by Prof. Kent, irregular results of 

 this kind must be expected, and it is quite possible 

 that a large series of observations would prove these 

 anomalous results to be of minor importance. The 

 simplicity of the tests and the ease with which they 

 can be carried out is a strong argument for their 

 adoption, provided that extended observation shows 

 that they yield constant results. 



THE CHILKA LAKE SURVEY.'^ 



THE object of the memoirs referred to below is to 

 inaugurate for the fauna of the brackish waters 

 and waters of fluctuating salinity of the Indian coasts 

 a register co-ordinate with that essayed by the Inves- 

 tigator for the Indian abyssal fauna. In the Chilka 

 Lake, which is one of the best-defined and most strictly 

 conditioned of these brackish tracts, and in the hands 

 of such skilled explorers and many-sided zoologists as 

 Dr. Annandale and Mr. Stanley Kemp, the under- 

 taking makes a singularly happy inception. 



The first instalment of the results of this Chilka 

 survey contains a most interesting introduction to the 

 topography and hydrography of the lake, and a de- 

 tailed account of its Sponges, Cnidaria, Ctenophora, 

 Oligochaeta, Echiuroidea, Polyzoa, and Cirripedia : the 

 introduction, the Echiuroidea, and the Ctenophora are 

 the joint work of both authors ; the short report on 

 the Oligochaeta is contributed by Col. J. Stephenson; 

 for all the other groups Dr. Annandale is solely re- 

 sponsible. The second instalment is composed of four 

 reports — on the Mysidacea, the Stomatopoda, the Mam- 

 mals, Reptiles, and Batrachia, and the Aquatic Insects 

 —the first being by Dr. W. M. Tattersall, and the last 

 containing a contribution by Mr. F. F. Laidlaw. 



The Chilka Lake is situated not far from the famous 

 shrine of Jaganath at Puri, at the Mahanaddi Delta 

 end of the tract of sand-waste, scrub, and screwpine- 

 swamp that lies between the Ganjam hills and the Bay 

 of Bengal. It is about forty miles long, with a maxi- 

 mum breadth of about sixteen miles, and a depth of a 

 few feet; and in its origin it is a silted bay which — 

 except for a mouth about 300 yards wide near the 

 north-easterly limit — has been finally cut off from the 

 sea by a narrow sand-spit formed (in the way usual 

 along the east coast of India) by the strong northerly 

 currents. By its narrow mouth it is in communica- 

 tion with the sea, while into the same north-easterly 

 end run some of the waning effluents of the Mahanaddi 

 Delta. 



The survey under report embraced all the cardinal 

 seasons of the year, and included 171 collecting sta- 

 tions. The observations show that in the wet season, 

 when the Mahanaddi is in flood, the water of the lake 

 is nowhere more than slightly saline, and over most 

 of the area is quite fresh ; while in the dry season it is 

 nowhere anything but distinctly brackish, and in all 

 the seaward area is as salt as the sea outside — facts of 

 the greatest interest in their biological bearings. 



The vegetation is considered mainly from the zoo- 

 logical point of view. Dense beds of Potamogeton 

 give shelter to certain kinds of animals, and the leaves 

 of a creeping Halophila afford anchorage to others; 

 these are the characteristic water-weeds ; for true sea- 

 weeds, of the higher kinds, are absent. At the water's 



1 Memoirs of the Indian Museum, vol. v.. No. i, July. " Fauna of the 

 Chilka Lake." By X. Annandale and S. Kemp. Pp. iii4-i46-(-ptateR. 

 Price 15 rupees. Vol. v.. No. 2, October. " Fauna of the Chilka Lak«.'' 

 Pp. 147-197-f-plates. Price 3.8 rupees. (Calcutta: Indian Museum, 1915. 



NO. 2409, VOL. 96] 



edge there is little encouragement for sedentary organ- 

 isms — no mangrove, and few screwpines, the most 

 conspicuous shore-growth being a tall reed (Phrag- 

 mit^). 



Beyond stating that the fauna as a whole is — as 

 might be expected — mainly of marine origin, and 

 specifying some distinctive features of the different 

 habitats to which it conforms, the authors for the pre- 

 sent make no generalisations outside the particular 

 groups dealt with in their initial reports. Among in- 

 teresting items it is noted that both fresh-water and 

 marine sponges are found growing side by side, the 

 former (Spongilla) being unable to resist high degrees 

 of salinity, but the marine forms seeming perfectly 

 comfortable in the wet season when the water is quite 

 fresh ; among the latter the world-wide Cliona vasti- 

 fica and the Japanese Suberites sericeus are common, 

 both producing gemmules in abundance. The Coelcn- 

 terates include eight or nine Hydrozoa, six Actinozoa, 

 a Scyphomedusa, and a Ctenophore. The last, like 

 several of the Hydrozoa, is a periodic visitor during 

 favourable conditions ; but the Scyphomedusa, though 

 a common inhabitant of the Bay of Bengal, has estab- 

 lished itself in the lake, and subsists, though in a state 

 of repose, even when the water is quite fresh. Two 

 species of Actinozoa {Halianthus limnicola and 

 Edwardsia tinctrix) and one Hydrozoon (Bimeria 

 fluminalis) seem also to be quite acclimatised, though 

 the two first-named are inclined to be torpid, but with 

 fecundity unaffected, in the fresh-water season. The 

 barnacles of the lake belong to two widely distributed 

 marine species, and also are inured to fresh water. 



The common species of Squilla and all the four 

 species of Mysidae found in the lake appear to adapt 

 themselves comfortably to all the seasonal changes of 

 salinity. In the account of the aquatic insects, Mr. 

 Laidlaw records as particularly noteworthy the exist- 

 ence in brackish water of the larvae of an Agrionid 

 dragonfly. The higher vertebrate fauna includes an 

 otter, a dolphin (Orcella), the gharial and another 

 crocodile, the hawksbill and edible turtles and a mud- 

 tortoise, and three species of water-snakes. 



The individual reports are instructive in fact and fer- 

 tile in inference ; all their regard for detail is infused 

 with discernment;' there is none of that assiduous 

 piling up of wearying and bewildering minutiae which 

 so often makes eclectic work of this kind stale and 

 unprofitable. 



The memoirs are illustrated by numerous text-figures 

 and twelve fine plates, which in the main are the work 

 of those accomplished artists, Abhoya Cham Chowd- 

 harv and Shib Chunder Mondul. 



A VEGETATIVE CRUSTACEAN.^ 



EVERY text-book of zoology mentions, as one of 

 the stock examples of degeneration, the curious 

 cirripede, Sacculina, which lives as a parasite on crabs. 

 Through the researches of Prof. Delage, more recently 

 confirmed and extended by Mr. Geofi'rey Smith, its 

 life-history is now well known. After passing through 

 free-swimming larval stages closely comparable with 

 those of the normal barnacles, Sacculina attaches itself 

 to its host and becomes endoparasitic, developing a 

 system of branching roots which ultimately permeate 

 all the organs of the crab. These roots radiate from 

 a central mass of cells within which the sac-like body 

 is differentiated, to emerge later on the surface beneath 

 the crab's abdomen. While Sacculina is, as a rule, 

 solitary, some related forms occur in considerable 



1 "On the Rhizocephalan genus Thomp«onia, and its Relation to the 

 Evolution of the Group." By F. A. Potts. Papers from the Department of 

 Marine Biology of the Carnegie Institution of Washington, vol. viii., 1915. 

 Pp. 32-f a plates. 



