i8 9 6. NOTES AND COMMENTS. n 



Professor Mitsukuri. Our readers are well acquainted with the 

 Chinese habit of eating Holothurians. Certain species only are 

 suitable for food, since many are rendered rather too indigestible by 

 the size and number of their calcareous stipules. The Beche-de-mer or 

 Trepang Fishery, as it is called, is largely carried on about the Great 

 Barrier Reef of Australia and in the China Sea (see Natural Scienxe, 

 vol. ii., p. 457). The particular species Stichopus japonicus also forms 

 an important article both of food in Japan and of export thence to 

 China, the value of the trade being estimated at ^100,000 a year. 

 At the instance of the Japanese Fisheries Commission, Professor 

 Mitsukuri has been investigating the life-history of this species, in 

 order to find some means of preserving, and, if possible, of pro- 

 pagating, the animal. He has already devised a plan and is having it 

 tried on a small scale. 



We are glad to learn from Professor Mitsukuri that the recent 

 war is likely to stimulate scientific activity in Japan. " The victory 

 is," he says, " in a certain sense the victory of science." 



The Cell-Theory. 



In the Quarterly Journal of Microscopical Science (Nov., 1895), ^ r - 

 Adam Sedgwick, in the course of reply to Mr. Bourne's criticisms, 

 makes some further remarks on the Cell-Theory which should be 

 read by all biologists. He distinguishes between the statement of 

 fact that " structures most conveniently called cells undoubtedly 

 exist, as the ovum, spermatozoon, lymph-cells, etc.," and the theory 

 that "organisms of Metazoa are aggregations or colonies of individuals 

 called cells, and derived from a single primitive individual — the ovum 

 — by successive cell-divisions ; that the meaning of this mode of 

 origin is given by the evolution theory, which allows us to suppose 

 that the ancestor of all Metazoa was a unicellular Protozoon, and that 

 the development of the higher animals is a recapitulation of the 

 development of the race." So far as the statement of fact goes, Mr. 

 Sedgwick thinks that the " phenomena called cell-formation " are not 

 of primary significance. He gave special instances of the absence of 

 this : in the mesoderm and in the formation of nerves ; and he 

 declared that the theoretical part of the cell-doctrine had led investi- 

 gators to misinterpret facts. Against the theoretical part of the 

 doctrine he continues to wage wholesale war, and most readers will 

 agree that he has made a reply to Mr. Bourne the occasion of urging 

 very weighty considerations against the older views. Incidentally, he 

 makes a novel suggestion as to the nature of the conjugating cells of 

 Metazoa. In the " Protozoa in which the amount of formed tissue is 

 generally slight, and the structure of the body simple, conjugation 

 can and does often take place between the ordinary forms of the 

 species." But in the Metazoa "conjugation is impossible between 



