A^ril 2^, 1878] 



NATURE 



509 



The Earliest Changes in Animal Eggs.— The 

 patient researches of van Beneden, Grieff, and Oscar 

 Hertwig have discovered many interesting facts in the 

 structure of simple ova when laid, the mode of fertilisa- 

 tion, and the first segmentation. Oscar Hertwigj's last 

 observations are on the starfish Asteracanthion {Morpholo- 

 gisches Jahrbuch, vol. iv. Part I.), and he describes the 

 changes as follows : — The germinal spot of the unfertilised 

 ovum first shows a separation into two portions, while 

 part of the germinal vesicle contributes material out of 

 which first one and then a second " directive corpuscle " 

 is formed. By this time the germinal vesicle is undis- 

 tinguishable, having left a small portion as the ovinucleus 

 {eikern). When fertilisation takes place, the spermatozoon 

 gives rise to a small body, the sperm-nucleus {sperma- 

 kern) ; this body approaches the ovinucleus, and they 

 fuse to form the segmental nucleus {Jurchtmgskern) ; this 

 precedes the division of the whole egg into two cells. If 

 such observations are extended to many species and con- 

 firmed by other observers, we shall have an important 

 gain in our knowledge of the results of fertilisation. 



Glacial and Post-Glacial Fishes of Norway. — 

 We learn from the Danish Naturen the appearance 

 in the third part of the Nyt Mas;azin for Natur- 

 videnskaberne, of a paper, by M. Robert CoUett, on 

 the glacial and post-glacial fishes of Norway. These 

 fishes, which are most perfectly preserved in chalk-lumps, 

 the outer shapes of which more or less perfectly exhibit 

 the outer shapes of the included fishes, are found in clay 

 deposits some 360 feet above the sea ; the fishes belong 

 all to the existing fauna, displaying at the same time their 

 Arctic and North Atlantic origin. Out of twelve species, 

 described by the authors, the most common is the Mal- 

 lotus villosus, which is found everywhere ; one species, 

 the Clupea sprattus, is worthy of notice, because it is now 

 a native of more southern waters. 



Poaching Birds. — Mr. N. B. Moore has made obser- 

 vations at the Bahamas on the Certhiola flaveola, which 

 obtains nectar from the flower of Verea crenata by thrust- 

 ing its bill at once through the petals into the nectary. 

 It is only after the bird has made an opening that small 

 black ants and other small insects are found in the 

 nectary. But these birds also poach on the woodpecker's 

 preserves. One day Mr. Moore observed a Picus varius 

 extracting sap from a logwood sapling, and as the wood- 

 pecker flew away, two Certhiolse appeared, perched near 

 the sap-pits from which the juice was oozing, and by 

 cunningly thrusting in their penicillate or bristle-tipped 

 tongues, commenced to lap or suck the fluid into their 

 mouths. This practice was constantly observed after- 

 wards. Mr. Moore fixed the bowl of a teaspoon in a fork 

 of the same tree, and placed some strained honey in it. 

 In three days the Certhiolae found this, and commenced 

 to feed on it. They were followed by another bristle- 

 tongued bird, Dendroeca tigrina, and other species, who 

 also attacked the woodpecker's sap-pits. These are 

 interesting instances of apparent intelligence on the part 

 of birds {Proc. Boston Soc. Nat. Hist., January, 1878). 



GEOLOGICAL TIME^ 



IF a rigid body be in rotation about an axis of symmetry 

 it will continue to rotate about that axis, but if it be 

 set spinning about an axis inclined to that of symmetry 

 the axis about which it spins will be continuously dis- 

 placed relatively to the body ; in other words, it will 

 wabble.2 This wabbling is well illustrated by the motion 

 of a top whilst it is " going to sleep." 



As the rotating body approaches more and more nearly 

 the spherical shape, so does the wabbling become slower 

 and slower. If the earth, which is nearly spherical, were 



I Abstract of a paper read before the Royal Society on March 14. 

 « I follow Dr. Haughton in the use of this very expressive word. 



to wabble in its diurnal rotation it would do so in about 

 305 or 306 days. 



Dr. Haughton has lately published^ an ingenious 

 speculation, founded on the possibility of the wabbling of 

 the earth, in which he seeks to determine limits to the 

 duration of geological time from the observed absence of 

 any motion of this kind. 



The object of the short paper, of which I am here 

 giving an account, was to combat the applicability to the 

 case of the earth of Dr. Haughton's results. 



The method pursued by him may be shortly described 

 as follows : — If a continent were to be suddenly upheaved 

 the earth's axis of figure (or strictly speaking, the principal 

 axis of greatest moment of inertia) would be displaced 

 from its previous position ; immediately after the earth- 

 quake, the axis of rotation being where it was just before 

 the earthquake, is no longer coincident with the axis of 

 figure, and therefore a wabble is set up in the earth's 

 motion. If it were not for frictional resistances that 

 wabble would continue for ever after. But it is easy to 

 see that, as the ocean is not rigidly connected with the 

 earth, a tide of 306 days period would be set up. This 

 tide would then rub on the sea-bottom, and would 

 gradually reduce the wabble and bring the earth " to 

 sleep " again like a top. 



By reference to the estimate of 'Adams and Delaunay 

 of the effects of tidal friction in retarding the earth's 

 rotation. Dr. Haughton endeavours to find a numerical 

 value for the frictional effect of such a 306-day tide as 

 above explained. He then finds how long it would take 

 to reduce a wabble of given amount to one of any smaller 

 amount. 



In a previous paper he had already shown that the 

 elevation of the continents of Europe and Asia must have 

 shifted the earth's axis of figure by 69 miles at the earth's 

 surface. If, therefore, such an elevation took place suddenly, 

 it must have started a wabble, in which the axis of rotation 

 described a circle of 69 miles radius round the axis of 

 figure. 



But Dr. Haughton is of opinion that astronomical 

 instruments are now so perfect, that a wabble of 5 feet in 

 radius would be detected, and that it is not, therefore, 

 permissible to suppose that the present actual wabble has 

 a radius of even 5 feet. His numerical calculations, then, 

 show that it would take 641,000 years to reduce the radius 

 from 69 miles to 5 feet by means of the tidal friction, and 

 he, therefore, concludes that, if Europe- Asia were manu- 

 factured per saltum, that event cannot have taken place 

 less than 641,000 years ago, and that it may have been at 

 a much more remote epoch. 



The improbability of this supposition induces him to 

 consider the case of elevation by 69 geological convul- 

 sions, each of which displaced the axis through one mife, 

 and where the radius of the wabble is reduced to five feet 

 between two successive convulsions. He here finds that 

 the elevation of Europe- Asia must have occupied 27^ 

 million years, and that no geological change altering the 

 position of the earth's axis through one mile can have 

 taken place within the past 400,000 years. 



He lastly supposes that the wabble has a radius of 

 5 feet, and that the geological changes take place at such 

 a rate that the increase of the radius is exactly destroyed 

 by friction during each wabble, so that the radius of 

 5 feet remains constant. On this supposition he finds 

 that the time required was 4,170 million years. 



Now it appears to me, from this method of treatment, 

 that Dr. Haughton is of opinion that a second earthquake 

 of elevation following a first would necessarily increase 

 the radius of the wabble. For if not, why does he pos- 

 tulate a lapse of time between successive earthquakes, 

 and in the last case make the supposition of the increase 

 of radius be exactly destroyed.? It is on this point 



' Notes on Physical Geology, No. III., Proc. Roy. Soc., voL xxrL 

 P- 534- 



D D 2 



