INVEKTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 705 



branous canal contained in a testaceous tube wbicb unites tbe parti- 

 tions ; or (4) the tube may be replaced by a number of superimposed 

 funnel-shaped tubes ; or, lastly, the tube may be interrupted and the 

 septa and chambers be traversed by a lime-coated membranous canal. 

 With regard to the last arrangement, which is that which is found in 

 the Nautdus, it is to be noted that the " calcareous incrustation is apt 

 to be dissolved by the acetous change of the alcohol," and it is this 

 which gives especial value to the observation of Professor Vrolik, 

 inasmuch as it had been previously supposed by some that the siphon 

 of the Nautilus might have a dilating and contracting action. The 

 paper concludes with some remarks on the vascular supply of the 

 siphon, and with some suggestions to the student who shall be 

 fortunate enough to be able to examine these foi-ms in their living 

 state. 



Eye of the Cephalopoda.* — Dr. Schobl, in an article on this sub- 

 ject, deals more especially with the vascular supply, in addition to 

 which he gives an account of what has been done by earlier authors ; 

 as will be gathered from the few words we can say, the arrange- 

 ments are difficult to make out in their completeness. Aroimd the 

 cornea there is a pair of greatly coiled arteries, and of veins ; outside 

 these there is a fringe, in which are small veins and arteries, and 

 outside this is the circulus arteriosus iriclis ; this last is bounded by a 

 fairly broad corona ciliaris, made up of about 160 closely aj) plied 

 ciliary processes. Then there is a ring of well-developed vessels 

 formed by a median artery with a vein on either side ; then the 

 ciliary plexus, and the well-developed posterior ciliary vein and 

 artery. External to the circular vessels we find the zona ciliaris, in 

 which are a number of venulce and of " recurrent arteries." 



Action of Strychnine on Gasteropodous Molluscs, f — Mr. E. 

 Heckel has presented to the Academy of Sciences an account of the 

 action of the salts of strychnine upon these Molluscs. 



Noting the fact that the alkaloids occur more frequently, and 

 possess a more powerful physiological activity, the higher we ascend 

 in the scale of vegetable life, he asks whether theii- special task may 

 not be to defend the plant against animal enemies, especially as the 

 more important an organ the more generally it is possessed of 

 poisonous properties. He therefore finds it important to ascertain 

 the action of the best-known alkaloids upon certain selected terms 

 in the animal series. For this purpose he has experimented with 

 strychnine sulphate and oxalate upon Helix pomatia and aspersa, and 

 Zonitcs algirus. He observed that whilst Helix aspersa of the mean 

 weight of 6 to 6-70 grms. succumbed to a dose of strychnine sulphate 

 of -025 grm., Zonites alcjirus of 8 grms. and Helix pomatia of 9-70 

 grms. perfectly resisted doses of • 045 grm. He concludes that the 

 Gasteropods enjoy a remarkable immunity from the eftects of strych- 

 nine ; that with them, as in the case of the Vertebrata, the degree of 



* ' Arcb. Mikr. Anat.,' xv. (1878) p. 215. 



t ' Comptes Rendus,' Ixxxviii. (1879) p. 018; 'M. .Journ. Sci,' 1. (1879) p. 514. 



