THE MUSEUM. 



23 



Ann Arbor were among the investigat- 

 ors at the school during its first year. 

 The labratory was housed in a two- 

 story frame building, and was support- 

 ed by donations. Year by year its 

 work has grown, the laboratories have 

 been enlarged, course after course have 

 been added to the curriculum, facilities 

 for investigation have been increased, 

 and the corps of scientists who spend 

 each summer their entire vacation at 

 this seaside institution studying marine 

 growths has grown larger. Nearly all 

 who have worked there, being biol- 

 ogists, have been believers in a chem- 

 ical theory of life. They have believed 

 that life originated on the earth 

 through the combination, in the course 

 of natural evolution of the world, of 

 the chemicals which compose simple 

 protoplasmic cells; that through the 

 long course of countless centuries these 

 growths have modified, influenced by 

 circumstances and the change of the 

 world about them, and have gradually 

 produced by natural means all that is 

 living on earth today. Species have 

 differentiated by natural means, and 

 from a single cell to a man there has 

 been a steady and a constant growth. 



This has been their theory. To es- 

 tablish it they have sought to produce 

 artificially that combination which be- 

 comes, instead of a mere combination, 

 a unit — a cell — and which has the pow- 

 er of moving itself and of growing and 

 reproducing itself. Toward this they 

 have wrought constantly, and step by 

 step they are approaching their goal. 



Among the workers at the school in 

 previous years W. N. Norman, profesor 

 of biology in the University of Texas, 

 was among the most ardent. Profesor 

 Norman discovered that if he added to 

 sea water, in which were the unfertil- 

 ized eggs of certain marine animals, 

 salts of magnesia to increase the water 

 to a certain density, the eggs began to 

 develope. They never produced larvae, 

 but grew into unformed masses of cells, 

 which broke up as soon as they were 

 placed in normal sea water. On this 

 Profesor Norman was at work a year 



ago when his efforts were ended by 

 an attack of typhoid fever which caused 

 his death in Boston. This segment- 

 ation of eggs of marine animals also 

 was accomplished by other students at 

 the laboratory. Seeing in it the pos- 

 sibility of great developments, Profesor 

 Loeb took it up where Norman left off. 

 His discovery is the result. 



The sea urchin is one of the com- 

 monest of marine animals. It is found 

 in great numbers along the shore of 

 the north Atlantic. To the casual ob- 

 server it consists of a ball of prickles, 

 about the size of a fist, which moves in 

 the water. Examined more closely 

 these prickles are found to be spines 

 projecting from a shell which has a 

 single small opening underside, in which 

 is the mouth of the animal occupying 

 the shell. 



As among fishes, there are among 

 sea urchins two separate sexes. The 

 female deposits her eggs in secluded 

 spots in the rocks along the shore, and 

 the deposit of milt fertilizes them. The 

 eggs, then left to themselves, hatch, or 

 develop, in a few hours into blastulas, 

 and grow thence through the gastrulas 

 stage to plutei. As plutei they live for 

 some time, just as a young frog exists 

 as a pollywog, at length appearing as 

 their parents did before them as sea 

 urchins, clad in shells and spines. 



For the purpose of his experiments 

 Prof. Leob secured eggs from a female 

 sea urchin which he was ceriain had 

 not been fertilized. These eggs he 

 placed in water containg solutions of 

 various salts. Calcium, sodium, potass- 

 ium, and magnesium were used. He 

 found that when he put the eggs in a 

 calcium solution no result was obtain- 

 ed. When potassium was used they 

 developed slightly. In sodium they 

 slowly evolved into blastulae, but in 

 magnesium solutions these later forms 

 were produced in two hours, and with- 

 in twenty four hours these blastulae, 

 having been placed again in normal sea 

 water, developed into active and vigor- 

 ous plutei. The experiments were a 

 complete success, and magnesium 



