371 



the Society, resigning the office of Recording Secretary, on 

 account of the pressure of other duties. ^ 



On motion of Dr. Durkee, it was voted that the thanks of 

 the Society be presented to Dr. Abbot for his efficient 

 and faithful services for the last five years, as Recording 

 Secretary. 



Dr. W. I. Burnett presented a paper " On the Develop- 

 ment of Mollusks in Holothuridse, as follows : 



I wish to call the attention of the Society to that remarkable 

 episode in the embryology of the Mollusca — the development 

 of certain Mollusks in Holothuridse. The facts of the case 

 were discovered and announced by J. Miiller, (Verhandl. der 

 Akad. zu Berlin, 1851, p. 628, (October 23,) and Nachtrag, p. 

 679, (November 13,) or in exlenso in Miiller's Arch. 1852, p. 1,) 

 and they are, indeed, so wonderful, that it is well they were 

 brought out by so reliable a physiologist and embryologist. 



The main facts, briefly stated, are as follows: — In certain 

 individuals of Synapla digitata, there are found from one to 

 three sac-like bodies in the cavity of the body, attached by 

 their superior extremity to the head, and by the lower end to the 

 intestine ; but this connection of the sac with the abdominal and 

 other organs, is one of simple contiguity, and not of any direct 

 communication. The upper portion of the sac is of a yellow, 

 and the lower of a green color ; the lower portion, moreover, is 

 intussuscepted, with a blind end, like an inverted finger of a 

 glove. It is in this sac-like organ that are developed true 

 Mollusks ; in its upper or more capacious portion are found both 

 testes and ovaria, in the shape of sacs, which are not attached in 

 any way to the main molluskigerous sac. These organs bear no 

 resemblance whatever to ordinary testes or ovaria, except in 

 their products, which are identical. When the ovarium is per- 

 fectly developed, it and its capsule burst and discharge the ova, 

 which are then contained in the main molluskigerous sac ; after 

 this, from fifteen to twenty ova become invested with a common 



