1870.] Zoology. 433 



Society has been raised to that dignity because he had confined his 

 studies to the molar series of Rhinoceros and Hyaena. Anything 

 -which will simplify this study and reduce it to the level accessible 

 to ordinary minds must therefore be hailed with pleasure, and the 

 method which Mr. George Busk has devised is exceedingly valuable 

 in that way. Mr. Busk proposes to convert number into form in 

 the case of teeth, for increase of twentieths of an inch in breadth 

 using extension of a line, just as the mathematician proceeds in 

 drawing a curve representing progressive phenomena. The paper 

 ruled in fine squares of a tenth of an inch or so, which physiologists 

 and others make use of in recording rises of temperature or increase 

 of movement at successive intervals, is employed by Mr. Busk. To 

 obtain the odontogram of any mammal, you mark off as many hori- 

 zontal lines as there are teeth in the molar series; let each division 

 on the horizontal lines made by the perpendicular represent, say a 

 tenth of an inch ; -then with compasses measure the breadth of your 

 first -molar, mark it with a dot on the first horizontal line in tenths 

 of an inch ; then measure the second and mark it on the second line, 

 and so on for all seven — if seven there be. Your dots will now bo 

 at various distances from the perpendicular zero line, according to 

 the breadth of each tooth : join the adjacent dots and you have an 

 irregular figure produced of definite form and characteristic of the 

 species. On the same set of lines you can now measure out tho 

 lengths, or antero-posterior dimensions of the same teeth, and pro- 

 duce a figure overlapping your first figure, equally characteristic, 

 the two together giving an exceedingly accurate and trustworthy 

 means of comparing the dental series in allied species. With re- 

 gard to the teeth of some of the large pachyderms Mr. Busk has 

 proposed certain points of measurement besides those of length and 

 breadth, which we may hope soon to see adopted. It would be an 

 inestimable boon to palaeontologists if Mr. Busk would found a 

 system of measurements for all mammalian teeth, and publish at the 

 same time an authoritative series of such measurements with odon- 

 tograms of all the known recent and fossil mammalia. It at any 

 rate might be done with Rhinoceros and the Carnivora to begin with. 

 The Zoological Position of Sponges. — It is not three years since 

 in chronicling the discussions to which the glass-rope sponge, Hya- 

 lonema, gave rise, we had to mention that Ehrenberg the great 

 microscopist — who still is in Berlin outliving his age — holds to his 

 old belief that Sponges are Yegetals. We have now to record that 

 Professor Ernst Haeckel, of Jena, proposes to associate the Sponges 

 with the Corals and Hydromedusae, bringing them under the group 

 Coelenterata. Haeckel has attacked in former years that hetero- 

 geneous assemblage which we still know as the Protozoa ; and he 

 removed from it the Infusoria proper, leaving the Sponges, the 

 Radiolarians, the Amceboids, the Forammifera, the Gregarines, and 



