335 



In Goniocidaris the interambulacral plates of the adult are approx- 

 imately hexagonal in form instead of pentagonal. "The relative form 

 of the plates in young Goniocidaris is almost exactly the same as in the 

 primitive type, Bothriocidaris." 



"The early stage in which we find a single interambulacral plate, to- 

 gether with two ambulacral plates, in each area is so important that it 

 is desirable to give it a name, the proteehinus stage. The protechinus is 

 an early stage in developing Echini, belonging to the phylembryonic period, 

 in which the essential features of the echinoid structure are first evinced. 

 . . . . This protechinoid stage of Echinoderms is comparable as a stage 

 in growth to a similar stage which is expressed in the protegulum of 

 brachiopods, the protoconch of cephalous mollusks, the prodissoconch of 

 pelecypods, and the protaspis of trilobites." (33.) 



Miss Smith (Mrs. Alexander Shannon) has shown very conclusively 

 the exact resemblance of the form of the young Pentremites conoideus to 

 the adult Codaster (52). In Codaster the conical form, narrowest at the 

 base and enlarging upward, is maintained throughout life. In Pentremites 

 only the early stages of growth have this form, while the adult is broadest 

 at the base and narrowest at the top. 



This evidence from development would, according to the theory of 

 recapitulation, indicate that Codaster stands in an ancestral relation to 

 Pentremites, and it is therefore of importance to the theory that Bather 

 (2) from other evidence has independently reached the same conclusion 

 as Miss Smith in regard to the relationship of the two forms. 1 



Among corals Beecher (5) has worked out the development of Pleu- 

 rodictywm lenticulare and concludes that the first neanic stage, in the 

 manner of growth and the structure of the corallum, is very suggestive of 

 Aulopora, and should be given considerable significance." Girty (21) conies 

 to the same conclusion from a study of Favosites forbesi, etc. 



Bernard (14) has shown that the coral colony in similar fashion to 

 the bryozoan colony and the graptolite colony behaves as an individual. 

 In another paper (13) he has recognized as the first growth stage of the 



1 Bather's conclusion was published in 1900, and Miss Smith's paper in 1906. 

 The latter, however, was not aware of Bather's views as to the relationships of 

 these two forms, so that the conclusions of the two workers, arrived at indepen- 

 dently and from different lines of evidence are all the more important and convinc- 

 ing. Bather says in a review of Miss Smith's paper that he considers Pentremites 

 as the "extreme link in the series Codaster — Pliaenoschisma — Cryptoschisma — Oroph- 

 ocrinus — Pentremitidea — Pentremites." 



