ON EGGS OF MARINE ANIMALS 9 



test contains a pigment which is a natural indicator: animals 

 whose color has changed from red to green are moribund; if the 

 water that contains them is green, the animals are deteriorating. 



For the experimental embryologist, knowledge of the breed- 

 ing-habits is indispensable for his work. Where these are 

 periodic — as is true for many nereids, for example — his task 

 becomes simple, as will be shown beyond. If the animals shed 

 their gametes at low or high tide, this too is valuable to know. 

 The late Dr. Gilman A. Drew made available for laboratory use 

 the egg of Cumingia by learning that these clams brought to 

 the laboratory in sand shed very quickly when Isolated in dishes 

 of sea-water. In many species of starfish the animals congre- 

 gate for breeding so that fertilization occurs soon after the dis- 

 charge of spermatozoa and eggs. 



Many animals, especially those living at great depths of the 

 sea, can not with profit be collected by the worker himself. 

 Here he must depend upon the collecting staff, the dredging 

 apparatus and boats of the laboratory. However excellent the 

 apparatus for the collecting may be, the factor of prime impor- 

 tance is the collectors. If these be Inefficient or untrustworthy, 

 the experimentalist will suffer because of the bad condition of 

 the animals furnished him. The collecting staif is thus very 

 important for successful experimentation. A loyal and devoted 

 collecting staff Is of inestimable value to the reputation of a 

 marine laboratory; one given to sabotage, preferring some 

 investigators to others, is a disgrace. Here the Investigator Is 

 not responsible for the poor results he may obtain; he is the 

 victim of an Inefficiency that is often not known to the laboratory 

 authorities. 



Whenever the experimental embryologist Is dependent upon 

 others for the collecting of breeding animals or of gametes, he 

 must be confident that the collecting is properly accomplished. 

 He should be sure that he has freshly collected organisms or 

 cells; if these be aged, he has now to reckon with age as an addi- 

 tional complicating factor in his experiments. It would be 

 difficult, I think, to over-emphasize this point. 



In the first place, most marine animals withstand transport 

 very badly especially during their breeding seasons; some with- 

 stand It not at all. Bonnevie reported results obtained on eggs 



