228 NATURAL SCIENCE. October. 



lining the "out-current" canals may, in some sponges, be altered collar 

 cells. Fortunately, not much space is devoted to these controversial 

 questions, which, after all, from the point of view of the exhibited 

 series, are only of academic interest. 



The series begins with a definition of sponges. Then follows the 

 description of a simple Ascon sponge belonging to the " Olynthus " 

 type, i.e., consisting of a simple thin-walled sac, opening at the top 

 by the ascule, and with the thin wall perforated by pores. Five tiny 

 specimens resembling little tags of white thread are exhibited, and by 

 the side of them explanatory water-colour drawings. Next follows a 

 short account of the canal systems, which, after the scheme of Vosmaer, 

 are grouped under four types, ascending from the simplest to the next 

 highly evolved. 



A series explanatory of the classification, which is based on the 

 nature of the skeleton, follows. The group is divided into two classes, 

 Calcarea and Silicea ; the Sihcea are divided into two sub-classes, 

 Hexactinellida and Demospongiae ; and the latter sub-class is divided 

 into four orders, Tetractinellida, Carnosa, Monaxonida, and Keratosa. 

 The various divisions are illustrated by typical specimens and dia- 

 grams. 



The results of Professor Dendy have chiefly been drawn upon for 

 describing the Calcarea, those of Professor F. E. Schulze for the 

 Hexactinellida and Keratosa, and those of Professor SoUas for the 

 Tetractinellida. The illustrations of the Monaxonida are mainly 

 original. Comparatively full descriptions have been given of the 

 Venus' Flower-basket, the Glass-Rope Sponge, the Crumb-of-Bread 

 Sponge, and the Fine and Common Bath Sponges. A very interesting 

 column is devoted to the Freshwater and Boring Sponges. 



Evidently the greatest care has been taken to render the labels 

 concise, and, at the same time intelligible. To this end several 

 changes are introduced into the nomenclature : for instance, " whip- 

 chambers " (Geissel-kammern) for " flagellated chambers " ; " in- 

 current " and " out-current " for inhalant, exhalant, excurrent ; 

 "derm " for the confusing expressions ecto-meso- or meso-ecto-derm. 

 The design of the whole series, and the manner of mounting and 

 arranging the specimens is very satisfactory, and the result does 

 credit to Mr. R. Kirkpatrick. 



Anders Retzius. 



On October 13 the centenary of the birth of the zoologist and 

 anthropologist, Anders Retzius, is to be celebrated in Stockholm, and 

 his son. Professor Gustaf Retzius, hopes, by that time, to have 

 completed the great work on the human brain, that has occupied his 

 energies for the last nine years. 



The Retzius family has had among its members so many 

 naturalists of eminence, that, to prevent confusion, we may recall 



