32G The American Naturalist. [April, 



many contrasts. Where Hatschek is brilliant, Lang is conservative; 

 Hatscliek gives generalizations ; Lang offers a mine of detail ; Hat- 

 schek has many novelties in classification ; Lang follows rather the 

 beaten track. In short Lang's work stands to-day the most useful 

 compendium of invertebrate anatomy in existence. When the other 

 portions are finished (which we learn from the author will be in 

 about two years) the whole will take a front rank among the text- 

 books of the world. 



Another work of somewhat different scope which deserves praise as 

 high as Lang's Anatomie, is the Comparative Embryology of the 

 Invertebrates 5 of Korschelt and Heider, of which two parts have 

 already appeared. In opening a work of this character one naturally 

 compares it with the classic work of Balfour, issued ten years ago. 

 Until the whole work is completed a satisfactory comparison cannot be 

 made, for while Balfour scattered many of his generalization- through 

 the accounts of the different groups, the young Berliners reserve more 

 for the special portion which has yet to appear. It is interesting to 

 compare the size of the two volumes in some detail as follows, keeping 

 in mind the fact that the page of Korschelt and Heider contains 

 about 25 per cent more than that of Balfour. 



Balfour. Korschelt & Heider. 



Sponges 12 pages. 18 pages. 



Coelenterates 31 " 84 " 



Annelids 38 " 65 " 



Other "worms" 47 " 80 " 



Enteropneusti 4 " 11 " 



Echinoderms 31 " 50 " 



Arthropoda 137 " 600 " 



This conveys some idea of the amount of literature which has been 

 boiled down into these two parts, for they must be regarded rather as 

 compilations than as philosophical works ; the philosophy is to come 

 later. We learn that the concluding part will include the Molluscs, 

 the Tunicates, Balanoglossus and Ampbioxus, in other words all that 

 are not in the strictest sense vertebrates ; as well as the general portion, 

 and that a year or two more must elapse before the whole is completed. 

 Thus it, together with the somewhat older Lehrbuch der Entwick- 



Dr. E. Korschelt and Dr. K. Heider. Specieller Theil. Erstes und zweiies 



