268 RITTER AND CROCKER 



A long list of genera and species of Asterids might be made 

 out in which the larvas are now known to attach themselves 

 more or less firmly, usually it appears, by this ' larval organ.' 

 Sometimes the substratum of attachment is an inanimate object, 

 and sometimes, as for example in Asterias spi'rabilis Perrier, 

 '91, it is the parent star-fish, and the organ of attachment is 

 called an ' umbilical cord.' 



What is greatly to be desired is much more exact and de- 

 tailed comparative knowledge of the way the organ is used, 

 and of its structure and relations in late larval and in post-larval 

 life. 



But as said above, we think we already have a sufficient body 

 of facts to amply justify the suggestion that ari7i A of Pycno- 

 ■podia is in some intimate way related with the larval organ of 

 the embryo. 



