ASTEROIDEA 



119 



ing gradually in size outwards. Plates outside the adambulacrals 

 generally small and not very regularly arranged in longitudinal 

 or transversal series. The number of spines in the groups on 

 the dorsal side rather variable. R = 4-5 r. Colour varying from 

 blood -red to yellow. Reaches a very considerable size, up to 

 10 cm. length of rays. 



In the large specimens the rays may be very much swollen 

 and broad ; such forms have been described as Magdalenaster 

 arcticus and referred to the family Cryasteridse. But all inter- 

 mediate stages towards the usual slender-rayed form occur, and 

 these large specimens, which occur mainly in the Arctic seas, 

 evidently belong to Henricia sanguinolenta. 



The variety curta Norman is described as having much shorter, 

 broader, and flatter arms than the typical form ; also their 



Fig. 70. — Henricia sanguinolenta (O. Fr. Miiller). Young specimen. Dorsal 

 and oral side. Nat. size. (From Danmark's Fauna.) 



texture is stated to be less firm. It rarely exceeds 2 inches 

 in diameter. Colour pale yellow. It was found between tide- 

 marks in Balta Sound. Renewed examination of fresh material 

 is necessary for deciding whether this form can be maintained 

 as a distinct variety. 



This is a brood-protecting species. The mother attaches 

 herseK by means of the tube-feet in the distal part of the 

 arms to a vertical rock wall, the underside of a stone or the 

 like, then raises the proximal part of the arms and thei disk 

 so as to form a closed cavity, into which the eggs are extruded ; 

 these lie free in the cavity, not directly attached to the 

 mother. The development takes ca. three weeks, during 

 which time the animal does not feed. The embryos do 

 not get any nourishment from the mother, but subsist 

 entirely on the contents of yolk in the eggs. If the sea-star be 

 removed from the eggs or the larvae these develop further in 



