299 



Edouard Van Beneden in the field, the knowledge of the 

 embryonic history of Arthro]3ods is being immensely in- 

 creased. There is, nevertheless, plenty to do for -those who 

 have the time and patience to enter upon these very difficult 

 inquiries. 



The Genetic Relationship behveen Ascidians and Veter brutes. 

 By Professor Kupffer, of Kiel, three plates, sixty pages. 

 ' Max Schultze's Archiv,' 2nd part, 1870. — In the January 

 number of this Journal we gave some account of the very 

 remarkable researches of Kowalewsky on the development 

 of Ascidians, and some confirmatory remarks of Kupffer. In 

 the present paper Kupffer gives his observations on the 

 development of Ascidia canina in detail, very beautifully 

 illustrated. The ova and young stages of this species were 

 obtained at Kiel at the end of July and during August, so 

 that those of our readers, who care to do so, can this year 

 follow out these observations on allied species. The eggs are 

 placed in a Avatchglassfid of sea-water for observation under 

 the microscope — a low power being used, and the chief 

 difficulty being to catch the required view of the ovum at 

 the particular stage in its early development which may be 

 desired, since the changes proceed rapidly. Professor Kupffer 

 gives full details on all points; we here would mention this, 

 that he has thoroughly satisfied himself as to the mode in 

 Avhich the nervous system first originates — a matter concern- 

 ing which Kowalewsky was a little uncertain. Kupffer has 

 clearly seen a groove form on the outer surface of the ovum, 

 extending from the opening of the alimentary cavity, and 

 spreading round the egg like a meridian. This deepens and 

 widens, and finally the cells close in above it, leaving it as 

 the primitive nerve-cavity within the embryo. The nerve- 

 cord originates clearly as an open canal which becomes 

 covered in by the growing together of its walls above, as in 

 Vertebrata. 



The History of the Development of the Siphonojjhora. By 

 Ernst Haeckel, 1869. — Professor Haeckel's researches Avere 

 made two years since in the Canaries ; they relate to the 

 genera Physophora, Crystallodes, and Athorybia of oceanic 

 Hydrozoa ; they are published in quarto, and illustrated by 

 fourteen beautiful plates, by the Utrecht Society of Art and 

 Science, by which body they have been crowned, and from 

 whom Professor Haeckel has received a prize. " All appear- 

 ances which accompany the individual developmental liistory 

 of the Siphonophora are to be explained solely by the palse- 

 ontological development of their forefathers." This was the 

 motto which Haeckel adopted, and in his work he has 



