8 



MARINE BIOLOGICAL LABORATORY. 



lusks these early divisions of the egg are 

 almost identical and that many correspond- 

 ing cleavage cells give rise to homologous 

 organs. Incidentally such work has shown 

 the close genetic relationship of the groups 

 named ; it has also set a new pace in em- 

 bryology. Now that we know the exact 

 cell origin of these layers and organs, it 

 will never again be possible in describing 

 the development of these animals to refer 

 the origin of certain organs to ' germ layers ' 

 merely, nor to refer the origin of these lay- 

 ers to certain general regions of the embryo. 

 The importance of this line of work, not 

 onlj' in the study of the groups named, but 

 also to the science of embryology as a whole, 

 is fully recognized both in this country and 

 abroad, and the credit for this service be- 

 longs iu large part to the Woods HoU Lab- 

 oratory. 



Other work of the greatest importance 

 has been done in the line of what has 

 been called ' physiological morphology.' It 

 would exceed the limits of this article to 

 give even a brief description of papers of 

 this class which have issued from tlie Lab- 

 oratory. A few of the more striking lines 

 of work, however, must be mentioned. 

 Much attention has been given to experi- 

 ments on the regeneration of lost parts in 

 various animals. In hydroids, sea-auem- 

 ones and worms these parts are some- 

 times reproduced in a normal manner, 

 while under different conditions a head 

 may be caused to develop where a tail be- 

 longs or vice versa. Another line of work 

 has been the grafting together of different 

 parts of animals. One member of the Lab- 

 oratory succeeded in grafting together in 

 almost every possible manner the pupa; of 

 diiierent moths and butterflies. Some of 

 these afterwards went through the meta- 

 morphosis and came out as ' Siamese twins,' 

 ' tandems ' with four wings, etc. Another 

 line of work, even more important, is found 

 in ' experimental embryology.' In one fa- 



mous experiment performed at the Labora- 

 tory, the eggs of the sea-urchin were arti- 

 ficially fragmented before they began their 

 development, and in this way twins, trip- 

 lets, or still more numerous larvte might be 

 produced from a single egg. If the frag- 

 ments of the egg were entirely separate, the 

 larvtc which developed were separate and 

 perfect, if they were united, the larvis were 

 united forming all kinds of double or mul- 

 tiple monsters. Other experiments have 

 shown that certain salt solutions will cause 

 unfertilized eggs to develop for a short time 

 in an irregular way^, and only last summer 

 Professor Loeb discovered that he could 

 cause the unfertilized eggs of the sea- 

 urchin to develop into normal larvre, in 

 short, could produce artificial partheno- 

 genesis in a phylum in which it has never 

 before been known, by treating them with 

 certain salt solutions ; this is certainly one 

 of the most remarkable biological discov- 

 eries of recent years. The lines of work out- 

 lined above, together with many which 

 could not here be mentioned, and which 

 have been actively prosecuted at the Woods 

 HoU Laboratory, have been substantial 

 contributions toward the solution of some 

 of the most fundamental problems of bi- 

 ology. 



Each j^ear a course of general lectures on 

 various phases of biological work is given 

 by different members of the Laboratory and 

 by distinguished visitors. These lectures 

 are usually brief accounts of important in- 

 vestigations, presented in a popular form. 

 A volume of these lectures is published 

 annually and the contents of the volumes 

 form a brief index to the multifarious 

 activities of the Laboratory' in research. 

 These volumes are not only important con- 

 tributions to knowledge, but still more, they 

 are brief and popular presentations of what 

 are often abstruse and difficult subjects, and 

 as such they appeal strongly to investi- 

 gators, teachers and general readers who 



