ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 877 



the trabeculae ; the arterial vessels are twisted, and wrapped round 

 each other and the venules, while the latter are, on the contrary, 

 straight ; a capillary network with very narrow meshes immediately 

 underlies the epithelium. 



Chemical Composition of the Ink of Cephalopoda.* — The same 

 author here adds to his observations on the ink-bag an account of the 

 composition of the ink of Sejna officinalis. It is odoui'less, slightly 

 saline in taste, alkaline in reaction. Under the Microscope it is seen 

 to contain a number of minute corpuscles floating in transparent serum, 

 and manifesting Brownian movements when placed in fresh water. 

 Of 100 parts of ink, the constituents are : — 



"Water 60 parts. 



Mineral substances 8" 613 „ 



Insoluble organic substances 30 • 536 „ 



Extractive matters 0-851 „ 



The mineral substances, as determined after calcining, include 

 calcium, magnesium, sodium, potassium, iron, and the acids, carbonic, 

 sulphuric, and hydrochloric acid, the absence of phosphoric acid being 

 noteworthy. After drying the ink, treating it fcst with alcohol, then 

 with ether, then with glacial acetic acid, subsequently washing and 

 leaving for some time under the action of alkaline carbonate of potash, 

 and again washing and digesting with hydrochloric acid, the extrac- 

 tive, albuminous, and mineral matters and the mucin were removed, 

 and a homogeneous black powder with a greenish metallic lustre 

 remained, insoluble in water, alcohol, ether, the alkalies, and the acids 

 (nitric acid, however, yields a mahogany-coloured solution, with 

 evolution of reddish vapours) ; it is bleached by chloride of lime and 

 chlorinated water. Acids and alkalies cause a kind of precipitation of 

 the suspended particles of pigment ; it gives off ammonia when heated 

 in presence of soda-lime ; it contains carbon, hydrogen, and nitrogen 

 in the proportions: — C = 53 '6 to 53 '9, H = 4 and a fraction, 

 N = 8 • 6 to 8*8; results which agree closely with those of Heintz 

 and others. 



Development of Neritina fluviatilis.f — F. Blochmann gives an 

 account of the earlier stages in the history of this Fresh-water Proso- 

 branch, which resembles the marine forms in having a large number 

 of eggs laid in one cocoon ; these cocoons are not, however, connected 

 together. In its cleavage state it presents much the same characters 

 as other Gastropods, but it is distinguished by the extraordinary regu- 

 larity of its separate stages. The first four equal blastomeres give 

 rise at the animal pole to the ectoderm, and from one of them there 

 is separated off a large cell, which, itself dividing, gives origin to the 

 mesodermal bands. The three other cells give off cells which by 

 dividing go to form the enteron ; the first four cells, richly laden 

 with protolecithin, long retain their original form and position, and at 

 last give rise to the liver. The author points out that there is here, 



* Comptes Rendus, xciii. (1881) pp. 96-9. 



t Zeitschr. f. wiss. Zool., xxxvi. (1881) pp. 125-74 (3 pis.). 



