PROGBESS OF MICROSCOPICAL SCIENCE. 235 



were made witli aniline sulphate, by which he determined the absence 

 of lignin in fungi and algae. It is found in a very few plant-hairs, 

 in all wood-cells, but never in cambium. Many bast-cells have 

 considerable lignin, but the sieve-cells hardly any. The most curious 

 observation was that the walls of pith-cells in many plants aro 

 liguified, and the medullary rays also.* 



The Boots of the Spinal Nerves in Elasmobranch Fishes. — This 

 subject, which is one of great difficulty, has been lately worked out 

 by Ml". F. M. Balfour, B.A. It seems that the posterior and anterior 

 roots of the spinal nerves arise as independent outgrowths from the 

 involuted epiblast of the neural canal. The outgrowths for the two 

 roots are at first quite independent of each other, and only unite at a 

 late period of development. The posterior roots are the first to 

 develop. An outgrowth arises on each side from the dorsal summit 

 of the neural canal, which the author believes to be unbroken 

 throughout its whole length. The outgrowths on the two sides are 

 at first in contact with each other ; and from each there springs a 

 series of processes equal in number to the muscle-plates. 



These processes are the rudiments of the posterior nerve-roots. 

 They grow ventralwards in contact with the side of the spinal 

 chord. 



After the formation of the posterior rudiments, the original out- 

 growths from the spinal chord cease to be attached to it along its 

 whole length, and remain in connection with it at a series of points 

 only, each of which corresponds to a posterior root. 



The result of these changes is the formation of a series of nerve- 

 roots, each attached to the dorsal summit of the neural canal, and all 

 of them united together dorsally by a continuous commissure, which 

 is the remnant of the primitive outgrowth from the summit of the 

 neural canal. 



Subsequently the points of attachment of the posterior roots 

 travel down the sides of the spinal chord, and finally remain fixed at 

 about one-third of the distance from its dorsal summit.f 



The Placentation of Hyrax. — On account of the difterences of 

 opinion which have been expressed on this point, the subject has been 

 minutely investigated by Professor W. Turner, who, in a paper pre- 

 sented to the Eoyal Society in December last, goes minutely into the 

 anatomy of this organ. He concludes that as " the placenta of Hyrax, 

 both in the form of its villi and in the mode in which they are inter- 

 locked between the intraplacental maternal laminte, so closely resem- 

 bles that of the domestic cat, and as these laminte remain in situ after 

 the membrane, which I have named the serotina, is peeled off the 

 placenta, there can be no doubt that they are shed at the time of 

 separation of the placenta. Hence Hyrax, in its placentation, is one 

 of the Deciduata. Whether the membrane just referred to is also 

 shed during parturition is more difficult to say. The fact that it 

 peels oif the uterus along with the placenta, when they are artificially 



* Vide ' Sitzimgsb. der kaiser. Akad. der Wissen.,' Ixx. i. 

 ■f See 'Proceedings of the Royal Society,' No. 165. 



