804 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



nearly absent in it, and the usual gill net-work entirely so. 

 Muscular prolongations of the tunic run into the curious 

 conical protuberances of the test. The nucleus is contracted 

 and small, like that of Salpa. This singular species is be- 

 lieved to be without living allies. 



Professor Semper lias published an interesting volume 

 upon the supposed homologies in the structure of articu- 

 lated animals and vertebrates. 



Echinoderms. 



Among recent contributions to the developmental history 

 of animals is a paper on the development of a sea-cucumber 

 {Cucumaria doliolum). After fecundation the nucleus di- 

 minishes, and becomes a mere drop of protoplasm, inside 

 which a germinal speck appears in an hour or two. The 

 segmentation of the yolk goes on until two hundred and fifty 

 cylindrical flagellate cells are formed. After the formation 

 of the single-layered blastoderm, the embryo breaks through 

 the egg-skin, and swims freely by means of its ciliated mem- 

 brane. As the flagella gradually disappear, its activity is 

 reduced to a backward and forward motion ; and when the 

 tentacles are protruded, it sinks to the ground, and moves 

 only by crawling. 



Important papers on the anatomy of the sea stars and 

 urchins have been published by R. Teuscher in the Jena 

 Zeitschrift, illustrated by excellent plates. The last num- 

 ber contains a useful resume of his researches on the circu- 

 latory, water, and nervous systems, and on the integument. 

 Dr. Carpenter has studied the structure of the Comatula 

 star-fish, with a note on the nervous system and muscles of 

 the sea-urchins. 



Professor Loven, of Stockholm, has published in the Trans- 

 actions of the Swedish Academy an elaborate work, in quar- 

 to, on the Sea-urchins (Echinoids), which is illustrated by an 

 atlas of fifty-three plates. The work is mostly taken up with 

 an account of the hard parts forming the shell of thaJEcJd- 

 nus, but also contains an account of certain bodies called 

 sphceridia, and an elaborate drawing and explanation of the 

 nervous and water- vascular systems of J3risso})sis l>/rifera, 

 greatly advancing our knowledge of the anatomy of these 

 animals. 



