6o6 NATURAL SCIENCE. ^ct.. 



Dr. Joubin gives figures and descriptions establishing the course 

 of the circulation in Waldheiinia venosa. It becomes apparent that the 

 lymph leaves the central heart and is received by the central aorta 

 and the two lateral vessels, reinforced en route by the stores collected 

 in the two supplementary hearts ; it courses through all the vascular 

 ramifications of the genital glands, falls into the general body-cavity, 

 and bathes the exterior of all the organs. The function of the central 

 heart is that of propelling the lymph in order that it may bathe the 

 innumerable pores of the digestive system. "It is, therefore, strictly 

 defined, a lymphatic heart intimately connected with the digestive 

 apparatus from which it is a derivation. " 



Dr. Joubin offers in conclusion some observations of less impor- 

 tance relative to the special histological structure of the voluntary 

 muscular system of Waldheimia venosa, which in all other respects 

 resembles that of other species of the genus. The muscles are 

 minutely striated. His memoir is well illustrated with twenty-six 

 figures. The diagram of the course of the circulation in Waldheimia 

 venosa (see p. 604) would be more readily understood if the lettering 

 were not reversed. It is a welcome instalment of the author's 

 researches on the general morphology of the recent Brachiopoda. 



The philosophical palaeo-biologist, or student of " still life," may 

 be said to commence his researches at the point where the embryolo- 

 gist, or student " from the life," ceases his observations. It is only by 

 a combination of the best results of both methods of investigation that 

 we can hope to deduce a rational and enduring systematic classifica- 

 ion of the Brachiopoda, and to solve the problem of their evolution. 

 A remarkable uniformity has already been established in the embryo- 

 logy of the ancient Silurian types and their modern descendants in the 

 memoirs of Morse, Brooks, Beecher, and Clarke. Adult conditions of 

 ancient fossil species are shown to represent the youthful and adoles- 

 cent stages of more modern forms. Interesting observations published 

 at intervals during the last three years on the " Development of the 

 Brachiopoda," by Mr. Charles E. Beecher, of Yale College Museum, 

 and Mr. John M. Clarke, Assistant Palaeontologist of the State of 

 New York, mark a new departure in this direction (7). These are 

 based on a careful study of the principles of growth, the acceleration 

 of development, and the effects of mechanical genesis. They record 

 the geological sequence of genera and species, and incidents in the 

 ontogeny or development of the individual and the phylogeny of the 

 race. 



In a recent article (g), Mr. Beecher describes the stages of growth 

 and decline, and applies to the Brachiopoda the nomenclature and 

 methods first employed by Professor Alpheus Hyatt in his remarkable 

 memoirs on the classificatory values of these stages for the Mollusca 

 in general and a branch of the Cephalopoda in particular (Genesis of 

 the Arietidae). The early embryonic stages of the Brachiopoda are 

 thus defined: — i, Protembryo ; 2, Mesembryo; 3, Metembryo; 4, 



