958 SUMMARY OF CUBRENT RESEARCHES RELATING TO 



funnels wliich open freely into the ccelom. Blood circulates in the stroma 

 of connective tissue, and chemical investigations are alone now wanting 

 to complete the proof of the reual nature of this much discussed organ. 

 This kiilnoy must be regarded as an annex of the water-vascular system. 

 After a short notice of the poison-glands the authors pass to a con- 

 Bideriition of the affinities of the Echiuothuridfe, and the phylogcny of 

 the Echinodermata. The former may bo regarded as an independent 

 sub-f roup of the Echinoidea, distinguished by the flexibility of the test, 

 the imbrication of its plates, the presence of longitudinal motor muscles, 

 small spines invested in tegumentary sheaths, and the great development 

 of the organs of Stewart. They are most nearly allied to the Cidaridse 

 on the one hand and the Diadematida) on the other, but of the three they 

 are the oldest. They share the imbrication of all the plates of the body 

 with the Palajcchiuida), which is only an early condition in the Cidaridro ; 

 in the great majority of the Perischoechinida) the test is flexible. In 

 some Astheuosomas the genital orifices are not yet connected with the 

 genital plates, as in most other Echinids. The apical area of A. urcns is 

 very like that of Paleeechiniis elegans, and appears to be of an older type 

 than that of the Cidaridfe. As to the absence of external gills in the 

 Cidarids, it is possible that they are present in the young and are lost 

 later on, and the possession of buccal clefts would support this view. 

 The investiture of the spines in tegumentary sheaths is an eminently 

 embryonic arrangement, for, as is well known, it is seen in the ontogeny 

 of all the Euechinoidea. The organs of Stewart in the Cidaridse are as 

 rudimentary as those of the Diadematidfe, and they arise from a common 

 source which is to be found in the Echinothuridfe. 



The authors bring forward a number of considerations which induce 

 them to support the view, not now suggested for the first time, that the 

 Eehinoids are derived from the Holothurians ; they think that Perrier's 

 observations on the development of Comatula advance the proof that tho 

 Crinoids may be referred to the same source. They have less to say 

 with regard to the Asteroids and Ophiuroids, but Agassiz has sho^Vll 

 that Asteroids pass through a Hulothuria-stage. As to the derivation of 

 these two groups from the Crinoids, the authors are content with a jest, 

 with so little seriousness do they regard it. 



Of the Holothurians the apodal forms are, in the judgment of the 

 Drs. Sarasin, the most ancient ; these may be derived from an unseg- 

 mented worm, while Balanoglossus stands quite close to them. The 

 apodal Holothurian is to the beautiful Actinomefra as the bud is to the 

 rose or the caterpillar to the butterfly. 



Renal Organs of Star-fishes.* — Dr. A. B. Griffiths has been able to 

 isolate uric acid from the clear liquid found in the five gastric sacs of 

 the common star-fish ; no urea, guanin, or calcium phosphate could be 

 detected. 



Anatomy of OpMurids.f — M. L. Cuenot has some notes on the 

 anatomy of Ophiurids. The epithelium of the body is distributed 

 irregularly in all except the Euryalida. The colours of Ophiurids are 

 due to very fine refractive granules which appear black with transmitted 

 light. In the forms which live, like Ophiothix and Astropliyton, in 

 stony places, there are small hooks on the sides of the arms, and the 



• Proc. Koy. Soc, xliv. (1888) pp. 325-7. 



t ATch. Zool. Expe'r. ct Gen., vi. (1888) pp. 33-82 (3 pis.). 



