THE STAEFISH SOLASTEE ENDECA. 3 



Page 

 Origin of Muscle-Jihrillce in larva, 47 ; muscle causing flexion &c. of preoral lobe, 47. 

 Ciliation, 48. 



IX. Mode of Obtaining and Eearins the LAEViE 48 



Spawning in the tanks at the Millport Marine Station, 48 ; arrangement to retain the ova 

 and to keep the larvae healthy in aquaria with sea-water circulation, and in smaller 

 aquaria under aeration, 48 ; larvse obtained in tow-netting, &c., 49. 



X. Sttmmaet, &c 50 



External characters, 50; development of cavities, 51 ; development of skeleton, 52; general 

 comparison with Crihrella, 52 ; relations with development of other Starfish, 53. 



Eefeeences 53 



Explanation oe Plates 55 



I. Structure and Position. 



IN the classification of Perrier (21) the Solasteridse form a Family of the Spinulosse, 

 one of the five Orders into which this author divides Starfishes. Asterina and 

 Crihrella, the development of which has been carefully investigated (12, 15, 18), come 

 within the same Order, but are in different Families, viz., the Echinasteridae and the 

 Asterinidse respectively. 



The system of Sladen (23) makes the Solasteridse one of the ten Families belonging 

 to the Cryptozonia, the second of his two great Orders of Starfish. Crihrella falls 

 within the same Order as a member of the Echinasteridae, but the Asterinidse are 

 included in the other Order, namely the Phanerozonia. 



As regards Solaster endeca, the following characters should be noted at this stage, 

 other points of minor importance being referred to later as occasion arises : — 



The normal number of rays is nine, but occasionally there are one or two more or 

 less. The madreporite is single, no matter what may be the number of rays. The 

 aboral skeleton forms a fine reticulum made up of small plates, many of which carry 

 bunches of spines. Gills are present everywhere in the interspaces of this reticulum 

 in groups of two or three. There are no pedicellarise. The tube-feet in each ray 

 form a double row. The mouth-armature is, on the whole, of the adambulacral type, 

 but the first ambulacrals are relatively prominent. The globular part of the stomach 

 shows folded radial lobes ; above it the usual radial cseca are given off from the 

 pyloric sac, each pair arising by a long common duct. There are two small bunches 

 of rectal caeca. The anus, though very close to the middle of the aboral surface, is 

 slightly excentric in the direction of the interradius which on developmental grounds 

 must be entitled V-VI (pp. 20, 23). Strong perforated interbrachial septa are 

 present in all the interradii. 



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