I. Morphological and Physiological Works of a General Character. 5 



The comprehensive work of Neumayr includes an important chapter on the 

 evolution of Echinoderms. The author interprets the apical system of the Silurian 

 Bothriocidaris as a closed ring of 10 plates which correspond respectively to the 

 ocular and genital plates of the Euechinoidea; and he therefore regards this ar- 

 rangement as the most primitive one for all Urchins, rather than the usual one of 

 2 alternating rings containing 5 plates each. The latter condition, appearing in 

 the otherwise embryonic Tiarechinus, is due to a falsification of ontogeny, possibly 

 owing to mechanical causes as appears to be the case in the other Echiuoderms. 

 - At the lower end of the body of Dendrocystites is a capacious downward exten- 

 sion of the perisome, covered with small plates which pass gradually below into 

 the normal singly jointed stem ; and the normal Crinoid-stem may therefore be 

 regarded as a specialised structure which became adapted to a fixed condition by 

 long continued modification of the centre of the dorsal surface of the body. 

 Mesites, with its ambulacra closed by plates both internally and externally, is in 

 the same condition as the embryonic Starfish, and one from which the Echinid type 

 could be derived by removal of the inner or subambulacral series of plates. The 

 adambulacrals of Starfishes perhaps represent the ambulacral plates of Echini, 

 while the marginals of the Asterids are interambulacral, and their quadriserial 

 arrangement would then indicate relations with the Palaeozoic Echini. The 

 Cystids are related to the Echini through Cystocidaris, to the Asterids through 

 Palaeodiscus and Agelacrinus. These intermediate forms display to some extent 

 the characters of all 3 groups, and so the Asterids and Echinids probably have a 

 common root; so also with the Blastoids and Crinoids which are related to the 

 Cystids through Cadaster and Cystoblastus and Porocrinus respectively. The 

 Crinoids fall into the groups Epascocr in en and Hypascocrinen, according 

 as the mouth and ambulacra are or are not sub-tegminal. The latter are descended 

 from forms with the characters of the former, as shown both in embryological and 

 in palaeontological development. The common type of the younger Crinoids (Pen- 

 tacrinus, Comatula] must have had 5 large orals. Speaking of the Palaeocrinoids 

 the author agrees with Carpenter and differs from Wachsmuth & Springer in 

 regarding the 5 summit plates ofCoccocrinus, Allagecrinus etc. and the proximals of 

 the Carnerata as representing the orals of Neocrinoids [see Bericht for 1887 Ech. 

 p 6]. He also considers the 5 interradial plates of Cyathocrinus as orals, a view 

 formerly held by the above named authors, but since abandoned. Cyathocrinus 

 alutaceus Ang. approaches the Camerata in the structure of the vault, but in other 

 respects is a typical Cyathocrinoid ; while C. multibrachiatus presents a transition 

 phase between the summit structures of C. and the recent Pentacrinus respec- 

 tively. Furthermore the Liassic P. briareus seems to have had a ventral sac like 

 the Poteriocrinoids, and the latter have relations with the Cystids through Poro- 

 crinus and Hybocystites. The mutual relations of the Echinoderms which are 

 known as fossils may be expressed in the following scheme : 

 Ophiuro-Asteridea^p ,. , ^,Blastoidea 

 Echinoidea"^ ^ ""Crinoidea. 



All the intermediate forms belong to the oldest deposits, and the transitions are 

 of such a nature that they indicate simple linear relationships. Neither Asterids 

 nor Crinoids can be regarded as the most primitive group, but rather the Cystids. 

 Among these some form like Mesites with numerous irregular plates, but regularly 

 pentamerous, or possibly only trimerous, ambulacra, would come nearest to the 

 probable ancestral type. The radial symmetry of the dorsal pole does not denote 

 an homology between Asterids and Echinids on the one hand and Crinoids and 

 Blastoids on the other. For it has been acquired independently in each case; by 

 the Echinozoa from the condition of a Cystid with many plates in which the dorsal 



