54 BULLETIN OF THE 



In Plate I. Fig. 1, t*, t 5 , g 2 , g, and g i are seen through the stomach of the 

 brachiolaria; gt 1 and t-, g 1 and*/ 5 , lie on the same side of the brachiolaria as the 

 observer ; g z and g 5 are seen in profile, and lie on the lower surface. 



In the figures where the ambulacrals are represented, they are made very much 

 darker than in nature, in order to illustrate diagramatically their relationship to the 

 other plates. All the figures were drawn with the camera lucida, reduced in size 

 in lithography. Where a single arm only is represented, it is to be remembered 

 that the unrepresented arms are in the same condition of development. 



PLATE I. 



Fig. 1. View of the posterior (anal) extremity of the body of a brachiolaria of 

 Asterias, showing the first appearance of the calcifications which ultimately form 

 the terminals and genitals. The greater part of the brachiolaria is not shown in 

 this figure. 



Fig. 2. A somewhat older brachiolaria, in which the brachiolarian arms are be- 

 ginning to be absorbed. The dorsocentral (dc) has just appeared. The specimen 

 from which this was drawn was no longer free-swimming, but was taken with a 

 pipette from the bottom of the jar in which the starfishes were raised. (Abactinal 

 view.) 



Fig- 3. A somewhat older starfish in which the brachiolarian arms are still more 

 reduced in size by absorption. (Abactinal view.) In this stage the radial canals 

 are seen through the body of the starfish, and the ambulacrals have just begun to 

 appear. 



Fig. 4. The same, slightly younger than the last. This figure shows the plates 

 only ; the soft parts, with the exception of the brachiolarian arms, are not 

 represented. 



Fig. 5. Lateral view of a brachiolarian younger than Fig. 4, showing position of 

 the anus, a, and the madreporic body, mb. The lower part only of the brachiola- 

 rian is shown. 



Fig. 6. Side view of a somewhat older starfish separated from its brachiolaria, 

 showing the relation of the madreporic body to the first genital, g. 



PLATE II. 



Fig. 1. View of a young starfish, from the abactinal side, in which the brachio- 

 larian arras are almost wholly absorbed, and the interbrachial notches have ap- 

 peared. The body of the starfish and of the brachiolaria is seen through the walls 

 of the animal. 



Fig. l a . Two rudimentary spines of the terminals in their primary form. The 

 part represented is one of the interbrachial notches. 



Fig. 2. A somewhat older starfish, seen from the actinal side, showing the 

 mouth, stomach, radial tubes, and plates with spines. 



Fig. 3. Young starfish, seen from the actinal surface, with the first ambula- 

 crals, oral ambulacral, am, well formed. The second pair of ambulacral rafters, 

 am 1 , are just beginning to appear. 



