ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 405 



wMcli have the same chemical function in the economy. The author has 

 noted simihxr facts in the Hirudinea, and has shown the relation borne by 

 the so-called hepatic tissue to the pigmented dermal ones. It is interesting 

 to prove, in animals where the circulatory apparatus does not contain blood- 

 corpuscles, that there is a migration of the corpuscles which seem to have 

 a chemical action in the phenomena of assimilation, respiration, and 

 excretion. 



S. Incertse Sedis. 



Rotifera.* — In Prof. A. G. Bourne's general essay on the Eotifera, the 

 most interesting point noticed is, perhaps, the relations of the trochal disc. 

 He accepts the view that the anus of veliger forms always forms so as to 

 leave the primitive ciliated ring (" architroch ") post-oral ; that this archi- 

 troch changes its position on the development of a prostomium, and that 

 the two lateral portions come to lie longitudinally. These may be sup- 

 posed to have coalesced so as to leave two rings — the one praeoral, cephalo- 

 troch, and the other post-oral, branchiotroch. Among Eotifers the simplest 

 condition is seen in Microcodon, where there is a single circumoral ring ; if 

 this be thrown into folds we get the conditions which obtain in Stephanoceros ; 

 further stages of complication through PMlodina, Lacinularia, Melicerta, 

 where both cephalotroch and branchiotroch are thrown into folds, lead to 

 Brachionus where the cephalotroch becomes first convoluted, and then dis- 

 continuous. With regard to their power of resisting desiccation. Prof. 

 Bourne expresses himself thus : " Many Eotifers exhibit an extraordinary 

 power of resisting drought. Various observers have dried certain species 

 upon the slide, kept them dry for a certain length of time, and then watched 

 them come to life very shortly after the addition of a drop of water. The 

 animal draws itself together so that the cuticle completely protects all the 

 softer parts and prevents the animal itself from being thoroughly dried. 

 This process is not without parallel in the higher groups." The Eotifera 

 must be kept apart from the Mollusca, Arthropoda, and Chsetopoda in our 

 systematic classifications. 



Key to tlie Rotifera.| — Dr. T. S. Stevens has prepared a key to facili- 

 tate the use of Hudson's and Gosse's Monograph on the Eotifera, and 

 including only the genera and species described in that work. The 

 intention is no doubt good, but the result is not satisfactory. It may 

 possibly be of use to beginners, but no one but a beginner would be 

 likely to make use of it ; for it is perilously artificial, resting sometimes 

 on a few comparatively unimportant characteristics. There are, too, obvious 

 mistakes. Apsilus is said to be a free-swimming or floating genus, whereas 

 it is a fixed one. Floscularia is set down as both a free-swimming genus 

 and a fixed one ; and though this may be defended because the genus has 

 one free-swimmer, or rather one bad adherer, yet it would be puzzling to a 

 beginner using the key. Again, Limnias and Melicerta are placed in the 

 same group with Floscularia and Stephanoceros, in spite of the wide diversity 

 in the position of the buccal orifice with respect to the body's longitudinal 

 axis, thus showing how artificial the plan of the key is. The real difference 

 in structure between Gallidina and Adineta, that of the corona, is entirely 

 missed, and the two genera (in the key) are made practically identical. 



* Ency. Brit., xxi. (1886) pp. 4-8. 



t Journ. Trenton (N.J.) Nat. Hist. Soc, 1887, pp. 26-43. 



