136 



HARDWICKE'S SCIENCE-GOSSIP. 



to have finally disappeared. The enclosing folds of 

 the mantle remain as a sack and perform their part, 

 producing the chitino-calcareous pen of the living 

 Dibranch, in which parts can be recognised as 

 corresponding to the pro-ostracum, and probably 

 also to the guard of the Belemnite. If this be the 

 case, if the pen of Sepia and Loligo correspond to the 

 entire Belemnite shell minus the phragmacone- 

 nucleus, it is clear that the sack which develops so 

 early in Loligo, and which appears to correspond to 

 the shell-gland of the other molluscs, cannot be held 

 to do so. The sack thus formed in Loligo must be 

 held to represent the sack formed by the primaeval 

 up-growth of mantle-folds over the young nautiloid 

 shell of its Belemnitoid ancestors, and has accord- 

 ingly no general significance for the whole Molluscan 

 group, but is a special organ belonging only to the 

 Dibranchiate stem, similar to — but not necessarily 

 genetically connected with — the mantle-fold in 

 which the shell of the adult Aplysia and its 

 congeners is concealed. The pen, then of Cepha- 

 lopods would not represent the plug of the shell 

 gland. In regard to this view of the case, it may be 

 remarked that I have found no trace in the embryonic 

 history of the living Dibranchiata of a structure 

 representing the phragmacone ; and further, it is 

 possible, though little importance can be attached to 

 this suggestion, that the Dibranchiate pen-sack, as 

 seen in its earliest stage in the embryo Loligo, etc., 

 is fused with the surviving remnants of an embryonic 

 shell-gland. When the embryology of Nautilus 

 pompilius is worked out, we shall probably, know 

 with some certainty the fate of the Molluscan shell- 

 gland in the group of the Cephalopoda." 



It will be gathered from the foregoing extract, 

 that Professor Lankester's difficulties are really with 

 the formation of the embryological shell-gland, or pen- 

 sack. Reasoning from other embryological data, it 

 would be expected the embryos of the modern 

 Loligo and Sepia would furnish some account of 

 their modifications from the original Nautiloid shell. 

 This it does not appear to do in a very clear manner, 

 as the various modifications are ancient enough to 

 have produced corresponding effects in the embryo ; 

 although the pen-sack of the Cephalopoda is exactly 

 identical with the shell-gland of other mollusca, a 

 shell is not developed, but in its place a chitino- 

 calcareous pen. 



The modern analogues of the Belemnites are 

 therefore the modified descendants of them. 



Since their appearance as Cephalopodous Molluscs 

 with an internal shell, modifying influences have 

 been at work, causing the disappearance of the 

 original Nautiloid shell by the deposition around it 

 of calcareous matter, which would originally have 

 been used for the formation of the shell. 



Other influences have also had their effects upon 

 the animals and their internal shells, giving rise to 

 our modern genera and species of cuttle-fishes. 



We have seen how the Belemnites were ushered in 

 at the commencement of the Liassic Period, and 

 how they have become modified by the ceaseless 

 interaction of influences, until, at the present day, 

 we have the representatives of cuttle-fish interests in 

 the Sepias, Octopi, and Loligos, etc., in the great 

 world of life ; and it is noteworthy to observe that 

 the Dibranchiata, not merely in numbers, but also 

 in size, bid fair in our day to rival the developments 

 of the past. To the interest which a complex 

 organization gives our modern cuttle-fish, may be 

 added the interest of a singular past history. 



ASTRONOMY AND METEOROLOGY. 

 By John Browning, F.R.A.S. 



AT the meeting of the Royal Astronomical 

 Society, held on 6th of April, Mr. G. F. 

 Chambers read a paper on a catalogue of red stars, 

 which he had compiled as a result of seventeen 

 years' observations. The catalogue contains upwards 

 of seven hundred stars, nearly six hundred of these 

 being visible in England. The stars are all above 

 the ninth magnitude, and only distinctly orange or 

 red stars are included. Scarcely one dozen stars are 

 decidedly maroon or ruby in colour. 



Many stars, mentioned by the two Herschels and 

 various observers as red, now appear of an orange 

 colour. Mr. Chambers points out that there is a 

 great difference in sensitiveness to colour in different 

 persons, particularly to colours approaching red. 



Mr. H. Grubb sent a paper on the choice of 

 instruments for stellar-photography. In this, he 

 gives as his opinion, that reflectors are better than 

 refractors for the purpose, because the field of view 

 is flatter in refractors than in reflectors, the distortion 

 appearing to be greater in photographs taken with 

 refractors than in those taken with reflectors. Mr. 

 David Gill described an attempt he is making at 

 the Cape of Good Hope to map, by photography, 

 the whole of the southern constellations. 



At the International Congress of Astronomers 

 recently held in Paris, it was arranged that a photo- 

 graphic chart of the whole sidereal heavens should 

 be constructed with telescopes of about thirteen 

 inches aperture. This principal chart will show 

 stars to the fourteenth magnitude. Another chart 

 from negatives with shorter exposures will be made, 

 showing stars down to the ninth magnitude. At 

 present, only the observatories of Paris, Algiers, 

 Bordeaux, Toulouse, Rio Janeiro, and La Plata have 

 agreed to take part in the work ; but it is supposed 

 that many others will do so when their governments 

 have consented to supply them with the necessary 

 funds. It is to be hoped that the consent of the 

 English Government will be given promptly. 



In June there is no darkness of night, but always 

 cither daylight or twilight. The length of true day- 

 light is 16 hrs. 13 min. on the 1st day of the month. 



