482 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



minute raadreporic plate (m.pl.). The post-larva, still 

 associated with the remains of the plutens (fig. 41), and 

 after complete separation therefrom (fig. 42), occurred fre- 

 quently in the plankton. In the former figure, taken 

 from the oral face of the post-larva, only a few of the 

 skeletal plates, including the oral halves of the basket- 

 like terminals, are represented; in the latter, taken from 

 the aboral face, the central, the five radials, and the 

 aboral faces of the five terminals are shown. A remark- 

 able circumstance in connection with this larva is the 

 frequency with which the gut and the coelomic vesicles 

 become aborted and disappear. With regard to the time 

 of its occurrence it may be stated that it has always 

 appeared along with that of Ophiothrix fragilis and with 

 ophiopluteus mancus. It occurred in considerable num- 

 bers in July, in the years 1907 and 1908 respectively, but 

 was very rarely seen in 1909 and 1910. It reappeared 

 in small numbers in September, 1911, was more 

 abundant in the same month of 1912, and was abundant 

 in July and September, 1913. In all the specimens of this 

 pluteus examined in the last-named month, all the 

 skeletal rods were traversed by a central canal, as shown 

 in fig. 39a. I have seen traces of this in other plutei. 



Mortensen (12) correlates with Ophioglypha textu- 

 rata (Lamk.) = Ophiura ciliaxris (Linn.) the larva shown 

 in fig. 43, PL VII. It may be at once recognised by the 

 linear series of perforations and blunt spines which 

 ornament the skeletal rods of the postero-lateral arms. 

 Compared with the size of the body of the pluteus all the 

 arms are rather short and stout, and their skeletal rods 

 bear blunt spines. This is one of the less common 

 ophioplutei; and I have hitherto seen only one specimen 

 in which metamorphosis had begun. It occurred 

 sparingly in Port Erin Bay in July and early August, 



