INVERTEBRATA, CRYPTOQAMIA, MICROSCOPY, ETC 451 



M'Coy noted tlu'ee in eacli plate of PaheecJiinus elegans ; in other 

 fossil species there have been seen from two to five pores. All these 

 observations seem to show that in this, as in so many other 

 characters, Asthenosoma approximates to the palaeozoic sea-urchins. 



Coelenterata. 



Anatomy and Histology of the Actiniae.* — An elaborate paper 

 by the brothers Hertwig is especially directed to increasing our know- 

 ledge of the nervous system of these creatures. Putting aside the 

 Spongife, it is necessary to presuppose from the activity exhibited by 

 the rest of the Zoophyta in the face of stimuli, and the wondrous degree 

 of conseutaneousness which their muscles exhibit in contraction, that 

 they are really provided with some kind of nervous system. As to the 

 Hydromedusse, we have now a certain amount of information ; but 

 the remarkable investigations of Kleineuberg and Van Beneden on 

 Hydra and Hyclradinia respectively, far-reaching as they are, require to 

 be repeated ; Eimer and Chun are not in accord as to the nervous system 

 of the Ctenophora ; but in both these groups more has been done than in 

 the Anthozoa. 



The AdinicB were chosen as the subjects of the investigation 

 because of their easy accessibility, their convenient size, and the 

 total absence of any calcareous skeleton. The authors found a 

 nervous system of extreme simplicity ; nerves and muscles are distri- 

 buted throughout the whole of the body ; they are very intimately con- 

 nected with the epithelial layers which cover the surface of the body 

 and line its internal cavity, while, at the same time, they are largely 

 influenced by the characters of the supporting lamelhi; of connective 

 tissue. The results are due, the authors think, in large degree to 

 their method of examination ; little can be done with the fresh tissues 

 which are too opaque and too contractile ; using the same mixture of 

 osmic and acetic acids as that which they employed in investigating 

 the Medusce, they were able to isolate not only the nerves, muscles, 

 ganglia, and epithelial cells, but were provided with thin lamella) of 

 the tissues. Whole animals or pieces were jilaced for five or ten 

 minutes in a large quantity of the mixture (•2 per cent, acetic and 

 •04: per cent, osmic acid in sea-water), and then washed for some 

 hours in • 2 per cent, acetic acid ; the macerated pieces were then 

 stained witli picrocarmine or Beale's carmine ; specimens may be pre- 

 served in glycerine and water to which a few drojis of strong carbolic 

 acid solution are added. The authors enter into further details as to 

 their treatment of the objects, and describe the effect of various jioisons 

 on the Actinia) ; the most successful method of killing tliem apjiears 

 to be to introduce tobacco smoke by a tube into the bell-jar imder- 

 ncath wliich they are placed ; they may then be treated with 

 chlorof(jrm, and so soon as they cease to react to cxterual stimuli they 

 may be safely placed in dilute reagents witliout any fear of their 

 changing their form. The last point to be borne in mind is that all 

 reagents act very slowly on their tissues. 



The first chapter of the " Special I'art " deals with the uuutomy and 

 * ' Jcii. Zciia(hr. Natiiiw.,' xiii. (IbTl') i'. 157. 



