MUSEUM OF COMPARATIVE ZOOLOGY. 3 



determine of which of these my brachiolariae are the young. As most 

 of the younger stellate forms were raised from brachiolarias captured 

 by surface tishmg, it is almost impossible to say definitely to which 

 species of Asterias they belong. I was not able to fertilize artificially 

 Asterias, although plenty of ripe ova were repeatedly found. The 

 difficulty seemed to be in all cases in procuring the males. 



The following mention of their time of ovulation may be of assistance 

 to those who have in mind a visit to the New England coast for the 

 study of Echinoderm embryology. 



1. The eggs of Ophiopholis were fertilized at Eastport, Maine, on 

 July 17th. The young of -4. squamata w^ere found at Newport, R. L, in 

 July, August, and September. 



2. Echinarachnius can be artificially fertilized at Newport in August 

 and September. The probable time of ovulation is the end of August 

 and the first weeks of September. Plutei are abundant iu September. 

 A specimen of Arbacia laid eggs at Newport iu August. I have found 

 the majority of the plutei of Arbacia in July. 



3. Large numbers of Leptasterias with attached young were taken 

 in Massachusetts Bay in April. Multitudes of a red pupa of some 

 Holothurian were collected at Provincetown in April. 



4. The pupee of Synapta are found sporadic at Newport in August 

 and September by surface fishing. The auricularice of Synapta are 

 found iu July. 



The material which has served for the following observations on 

 the starfish young was collected iu two ways. The younger forms in 

 some instances were raised from the brachiolari?e, collected by surface 

 fishing with the Miiller net. This material includes all stages from 

 the first appearance of the plates, or calcai'eous skeleton, up to the 

 young starfish with three pairs of ambulacral rafters. The remaining 

 specimens, from the young Asterias with three pairs of ambulacrals 

 into the oldest stages figured, were found on the under side of stones 

 near low-tide mark. The large stones near the outer landing-place at 

 the Laboratory were turned over, and the young starfishes were found 

 clinging to them. This method of collecting involves continued search, 

 as Asterias is not common in the immediate neighborhood of the 

 Laboratory. 



The method by which the preparations of starfishes described in this 

 paper were made is as follows. The young starfishes were killed in alco- 

 hol (.35%). They were then rapidly passed through different grades 

 (50%, 70%, 90%) to absolute alcohol. They were then clarified in 



