6 DR. TH. MORTENSEN. 



pores persisting only a short time, the right being closed again 8-12 

 hours after its formation. Though I have not paid attention to this on 

 examining the living larvae, I think I can say definitely that the forma- 

 tion of two pore canals is not a normal process in the larva of A. glacialis. 

 In the larvae which I preserved on the 16th June, at 9 p.m., the enterocoel 

 vesicles have not been formed ; in those preserved on the 17th, 10 a.m., 

 they are formed, and the left vesicle alone has a pore. It is certainly 

 very improbable that the pore of the right vesicle should then already 

 have disappeared completely; this process would in that case go much 

 faster than Field has found it in A. vulgaris. It seems to me that the 



Fis. 5. 



Fig. 6. 



Figs. 5-6. — Bijnnnaria of Asferias glacialis, showing aLiiormal forniatiou of 

 dorsal pores. Seen from the dorsal side. 100/1. 



facts here produced rather tend to show that what Field has found is an 

 abnormality. In any case the two pores in the A. glacialis larva repre- 

 sent an abnormality. To enter on a discussion of the possible phylo- 

 genetic importance of the two dorsal pores is not the place here. 



I must also mention the observation that the larvae of this species, as 

 well as of all the other species reared, in swimming rotate around their 

 longitudinal axis, always turning to the left. In the Spatangus and 

 OpJiiactis larvae this rotation ceases along with the development of the 

 long processes ; in the other larvae it had not ceased in the most advanced 

 stages observed. 



II. — Luidia ciliaris. 



This species at first caused me a good deal of trouble. Both females 

 and males were found with ripe genital products, but the spermatozoa 

 did not move. Being myself not familiar with ex]3erimental work on 

 fertilization, I asked Mr. J. Gray, who was working at the laboratory, 



