4 BULLETIN OF THE 



clove oil, and mounted in balsam. Those which were stained were 

 carried from 70% alcohol into Grenacher's alcoholic borax-carmine, 

 washed, afterwards placed in from 90% to 100% alcohol, then removed 

 to clove oil and balsam. The preparations mounted without staining 

 show very well the relation of the plates to each other, but it is 

 necessary to use a staining fluid to bring out the tissues of the organs 

 in the immediate vicinity of the calcareous skeleton. 



In the study of the plates on the abactinal side of the disk of older 

 specimens, it was necessary to separate the arms from the disk proper. 

 No dissection was resorted to in this separation, for the arms are easily 

 broken from the disk along the suture between the first dorsal plate 

 and the second dorsal radial, leaving the former, as well as the genitals 

 and all intermediate plates between them, on the disk with the dorso- 

 central. In older stages staining fluid was used, but the best results, 

 as far as the plates are concerned, were obtained in specimens where no 

 artificial staining was resorted to. 



The use of chloroform, which gave good results in Amphiura,* was 

 not resorted to in Asterias. 



2. General Changes in External Form brought about by the 

 Growth of the Calcareous Plates. 



By the growth of the calcifications in the growing Asterias the animal 

 assumes a stellate outline, passing into this form from a spherical or dis- 

 coid larva. These changes are almost wholly the result of change in form 

 or modification in the an-angement of the plates, but the peripheral 

 appendages, spines, pedicellarise, and spicules also play an important part 

 in this growth. When the growth of the primary plates begins, the 

 young starfish is not stellate in form, and all the early plates are con- 

 fined to the body. The elongation of the arms are the most prominent 

 results of the modification in the shape of plates, of addition to those 

 already existing, and of enlargement of the same. In the growth of 

 the arm no marked symmetry in the formation of plates on the actinal 

 and abactinal regions of the arm was noticed. There is also no sym- 

 metry observed in the gi'owth of the calcifications in the actinal and 

 abactinal regions of the body. 



It is not in the province of this paper to give more of the develop- 

 ment of Asterias than is necessary to understand the relation of the 



* I tried a few specimens of tlie young Amphiura with clove oil, and find that 

 this reagent clarifies them better than chloroform. 



