Septembkb, 1801.] 



KNOWLEDGE. 



209 



Zoological. — For some tinic Dr. G. L. Johusou lia.s 

 been engaged in stiulying the inUnnal stnieture of the 

 eyes of ninnunals under the ophthahnosi-ope, and the 

 results of liis investigation, illustrated by thirty coloured 

 plates, liavo been published in the /'/(//. Trmix. Great 

 variation in the arrangement of the blood-vessels, as 

 well as in the colour of the retina, ai-e noticeable; blue 

 and violet seem to be unknown, while red. yellow, and 

 green form the predominating shades. In the main, 

 the various types of minute ocidar structure correspond 

 very closely with the different groups into which 

 mammals are now divided : this correspondence afford- 

 ing important testimony in favour of the general cor- 

 rectness of onr scheme of classification. Among the ex- 

 ceptions are the South American squirrel-monkeys, whose 

 eyes approximate in structure to those of the lemurs. 

 In regai-d to the range of vision possessed by different 

 animals it is mentioned that man and monkeys alone 

 possess parallel and convergent vision of the two eyes. 

 On the other liand, divergent and conse<jucntly very 

 widely extended vision is a prerogative of the lower 

 mammals: squirrels, for instance, and probably also 

 hares and rabbits, being able to see an object approach- 

 ing them directly from behind without the necessity of 

 tiu'uing their heads. 



A most remarkable discovery ha,s recently been made 

 with regard to the earliest and most primitive whale — 

 the extinct Zftii/Ziidoii. In association with the remains 

 cf this creature have been discovered on more than on<^ 

 occasion solid bony plates, which have been regarded 

 as fomiing the dermal armour of a turtle. It is now, 

 however, demonstrated that the plates in question belong 

 to Zeiiglixlon itself, which appears to have haxl dermal 

 ai-mour on the back-fin and certain portions of the back 

 somewhat resembling that of the South American 

 glyptodont armadillos. Traces of a similar armour 

 occur in an extinct Croatian dolphin, and tubercles 

 found on the back-fin of the common poi^jioise and on 

 the back of the Japanese ydijihucnita may doubtless be 

 regarded as the last remnants of this structm-e. As a 

 partial armour would be useless, it may be assumed that 

 the ancestral cetaceans were fidly protected by bony 

 plates. But such a rigid panoply would obviously be 

 unsuitable to a pelagic type, such as ZniiilDdun seems 

 to have been, and it is accordingly presumed that the 

 armour was restricted to part of the back of that animal. 

 The presumption that the ancestral cetaceans were fully 

 armoured must not. however, be taken to indicate that 

 they were descended from mail-clad land animals. On 

 the contrary, they themselves developed the armour, 

 which may have lieeu for the puipose of protecting them 

 from the breakers and the attacks of shai-ks when thev 

 led an amphibious life on the coasts. These interesting 

 investigations are by Dr. O. Abel, and appear in a i-eccnt 

 issue of the Bvitraije zur Pfilao/iioloyie und Geoloijic 

 Oeterreich- UiKjuyns. 



It was recently stated in an official report that salmon 

 do not feed while in fresh water, being afflicted during 

 their sojourn in rivers with a disease of the lining 

 membrane of the alimentary tract. Later olisei-vations 

 discredit the correctness of this view, evidence having 

 been adduced that river salmon catch and digest 

 minnows and other fish. The presumed disease of the 

 lining of the stomach is stated to be owing to the fact 

 that the fish examined were not sufficiently fresh. Still. 

 the fact is not disputed that during the time spent in 

 fresh water salmon maintain themselves to a very con- 

 siderable extent on the store of fat accumulated in 

 their tissues during their marine life. 



In Tlir (,'rii/i/iir of August ^id appears an excellent 

 ligure of the head and neck of a jircsumed new typo 

 of giraffe obtained by Sir llai'ry Johnston in north- 

 east Uganda. In addition to an ajojjaieiitly (llstiiicl 

 type of coloration the male of this giralfe possesses a 

 pair of low jnominences behind the large horns, so that 

 it is called by its discoverer " live-horned." The saim- 

 issue of the Journal contains a coloured illustration of 

 the new mammal — the Okapi {Okn/tiit JiJiiis/diii). 



Much interest attaches to an article on mothcr-of- 

 l)earl oysters, by Dr. If. L. Jameson, which appears in 

 the August i.ssue of the Pruccidlnyf; of the Zoological 

 Society. The enquiry has been based on the large series 

 of these shells in the collection of the British Museum, 

 and its inception was suggested by Professor Ray 

 Lankesler. Perhaps the most remarkable circumstance 

 connected with the investigation is the discovery that 

 the large Austro-Malayan oyster, the valuable " silver- 

 lip " and " gold-lip ' of commerce, is a distinct and 

 hithert,o unnamed species'. For this form the name 

 Maryiiritlffra iiiarima is appropriately suggested. 



Another important item in the same journal i,i a 

 memoir by Dr. A. Smith Woodward on extinct reptiles 

 from Patagonia. The forms described include a tortoise 

 belonging to the genus MiolnnUi. hitherto known 

 only from the Plistocene of Australia; a largo snake 

 closely allied to an existing South American type, and 

 a carnivorous dinosaur related to the European Megalo- 

 xtitiriis and the North American Oeralosaurus. The two 

 questions of most general interest discussed in this 

 communication relate to the apparent mixture of types 

 elsewhere characteristic of widely separated geological 

 horizons in Patagonia, and to the conclusions to bo 

 drawn from the occuireuce of closely allied forms in the 

 Australian and Patagonian Tertiaries. As regards the 

 former point it seems either that dinosaurs survived in 

 South America int^ the mammalian period, or that 

 some confusion has been made between the reptiliferous 

 and mammaliferous beds. As regards the latter, it is 

 suggested that the tortoise may have reached the one 

 hemisphere from tlie other by way of the Antarctic 

 continent. On the other hand, " it is just possible that, 

 if the direct ancestors of Miolania were known, this 

 remarkable chelonian would prove to have originated 

 not on any old Antarctic continent, but in some other 

 region of the globe from which scattered sui-vivors 

 wandered into the lands now named South America 

 and AiLstralia respectively." 



CURRENT CARCINOLOGY. 



By the Rev. T. R. R. STEUuiNtv, m.a,, K.it.s., I'.L.s., f.z.s. 



In the oldon time the history of nature was written at 

 less length and with less continuity than at present. 

 Like the " resting-eggs " of Entomostraca subjects were 

 allowed to have a period of quiescence, of peaceful 

 oblivion, before hatching out into new activity. We 

 moderns have changed all that. Be the subject what it 

 may, the discussion of it flows on without ceasing. No 

 one steadily watching that flow would expect it to fail 

 and be cut off. Nevertheless, like the stripling who " in 

 a showerful spring stared at the spate," a novice 

 suddenly confronted with all that has recently been 

 published on the class of cnistacea might well give a 

 gasp of surpri.se. For this, as for other classes of the 

 animal kingdom, tliere are various records which keep 



