IJAN 22 1898 



3. Synapta Vivipara : A Contribution to the Morphology of Echinoderms. 



By Hubert Lyman Clark. 



(Read November 3, 1897.) 



1. Introductory 



2. History and systematic position of Synapta vivipara 



3. Distribution and habits 



4. Fertilization and .segmentation of tlie egg 



5. Gastrulation and formation of tlie liydroeoel and 



coelomic vesicles 



1. Introductory. 



In February, 1890, through the kiudne.ss of Dr. W. K. Brooks, there were placed in 

 my hands for study a number of specimens of a small brown Synapta from Jamaica. In 

 their body-cavities there were numerous young ones in all stages of development, so that 

 an excellent opportunity was offered for working out the embryology. So interesting 

 did this prove that I gladly availed myself of the privilege of spending the months of 

 May, June, and July, 1896, at Port Henderson, Jamaica, in the marine biological labora- 

 tory of the Johns Hopkins University. For such a privilege I am under the greatest 

 obligations to the authorities of that institution. During those months, I studied the 

 segmentation of the egg and the early stages of development from living material and 

 obtained an abundance of preserved material for further investigations. Since my return 

 I have been engaged in a detailed study of the development and anatomy of the animal 

 under the direction of Dr. Brooks, and it gives me great pleasure to acknowledge the debt 

 I am under to him for his suggestions and help. 



The young were easily procured by cutting off the heads of the adults and thus 

 setting free the contents of the body-cavity. They could then be killed as desired, but 

 young taken from the body-cavities of preserved adults were fully as satisfactory for all 

 purposes. The best results were obtained by the use as a fixing agent of " corrosive- 

 acetic " (four parts corrosive-sublimate and one part glacial acetic acid), but excellent 

 preservation, especially for the adults, was secured by the use of picro-sulphuric or picro- 



