2 E. W. MacBEIDE and J. C. SIMPSON. 



of 12| diameters by the aid of the camera lucida, and then, after double imbedding in 

 celloidin and paraffin, were cut into serial sections and stained with Delafield's 

 hsematoxylin. • 



In the succeeding pages the four species will be taken up and described in detail. 



1. ASTERIAS BRANDTI. 

 Asterias brandii, Bell, P.Z.S., 1881, pp. 94 and 506. 



The young of this species contained in the collection consist in a brood " born* 

 after the capture of the mother," which was taken in McMurdo Bay, February 13th, 

 1902. 



The parent was identified by Professor F. Jeffrey Bell as A. brandti, but as it was 

 not sent with the embryos, nothing definite can be said as to its " brood-care," except 

 that this species must now be added to the list of viviparous Asteroidea. It is 

 probable, however, that according to the analogy of its family, the young are attached 

 to the lips of the mother during the earlier stages of development. 



All the embryos of this brood are of approximately the same stage ; the difference 

 between the youngest and oldest being simply a matter of size. The youngest is 

 shown in Fig. 1, which gives a ventral view. It measures 2*4 mm. from the centre of 

 the disc to the tip of the arms, while the radius of the disc is 1 • 5 mm. (E. = 2*4 mm., 

 r. = 1*5 mm.). The only external trace of the embryonic condition is in the closed 

 mouth and the small pre-oral lobe or larval organ. The oldest embryo is much larger 

 than the preceding (R. = 3 • 2 mm., r. = 1 ' 6 mm.), but apart from the smaller size of the 

 pre-oral lobe there is little difference. Internally, too, there is little difference in the 

 development of the organs, so that they may very well be described together. 



As may be seen from the figure, metamorphosis is complete in these young starfish, 

 and an examination of serial sections shows that the internal organs have nearly all 

 attained the adult relations. As these relations are, moreover, practically the same as 

 those in a young Asterina gihhosa of the same stage, it will only be necessary to mention 

 here the few points which show peculiarity. 



In the first place it will be noticed that the great size attained before the mouth 

 and anus are formed must be looked upon as an expression of the favourable conditions 

 under which development of this species proceeds. Another indication of the same 

 thing may be seen in the amount of yolk which still remains in the closed gut, and 

 which may even be seen outside the gut in the space between its dorsal wall and the 

 inner wall of the coelom. 



The pre-oral lobe (larval organ) in the oldest stage is little more than a vestige, 

 but in the youngest its connection with the inner perihsemal ring can still be traced. 

 The water- vascular system is well developed, and one can follow it quite easily in 

 vertical sections. The madreporic pore, pore-canal, and stone-canal may be said to 

 have assumed the adult relations. The axial sinus can be seen adjacent to the stone- 



