466 SUMMAEY OF OUREENT RESEARCHES RELATING TO 



where both central and peripheral ; " the ring has only a more central- 

 izing influence than any other part of the nervous system. 



Circulatory and Respiratory Organs of the Ophiuroidea.* — 



M. N. Apostolidcs, by injecting several species, finds that after 

 successful injection of the aquiferous system, and on dissection of 

 the interbrachial space of the madreporic plate, he meets with a 

 dilated whitish canal, the walls of which are kept rigid by calcareous 

 plates. On opening this canal there is seen, near the middle, a 

 brownish mass — the so-called heart, and by its side is a thread-like 

 tube — the true sand-canal, containing the injection. The so-called 

 heart is independent of the water-system, while the delicate canal 

 allows this system to communicate with the exterior. A careful 

 dissection of the " heart " shows that it is elongated and continued 

 into a canal which passes to the madreporic plate, on which it opens ; 

 its structure reveals it to be a gland, with an excretory canal. On 

 each side of it there are two small fibrous bands, which pass laterally 

 to the base of the arms ; like the bands which support the Poliau 

 vesicles, they are coloured by hsematoxylin, but the liquid injected 

 into the " heart " never passes to them. 



If the injection enters between the integument and the digestive 

 tract, that is, into the body-cavity, it is never seen on the exte- 

 rior, and does not penetrate into the water-system ; the body-cavity, 

 then, is entirely closed ; it consists of an enlarged portion which 

 surrounds the digestive tube, and of a flattened portion which is 

 found in the dorsal region of the arms. There is also a perineural 

 si^ace, as well as a radial cavity, and these enter into communication 

 with the general cavity ; there is no system of canals proper. 



A living animal may be observed to dilate and contract its dorsal 

 surface, and if colouring matter be put into the water, a double 

 current may be seen around the genital clefts. If a coagulable liquid 

 be injected by one of these, it is seen that the cleft opens into a large 

 and completely closed sac, which is dilated in the ventral and 

 diminished in the dorsal region ; these sacs, to which Ludwig has 

 given the name of bursfe, have so close a relation to the nutrient 

 fluid of the general cavity that they ought to be considered as 

 respiratory sacs ; the blood would appear to be drawn into the cavity 

 around the digestive tube (" peristomachal space ") by the alternate 

 contraction and dilatation of the sacs. 



Stomach and Genital Organs of Astrophytidse.j — Under the 

 above title Professor T. Lyman gives an account of his observations, to 

 which he was led by making a section of a gravid Gorgonocephalus 

 Pourtalesi of the ' Challenger ' collection : " My astonishment was con- 

 siderable when there was brought to light an internal economy which 

 reminded one rather of an orange than of an Echinoderm. A hori- 

 zontal cut, just above the joint of the radial shields, disclosed a 

 quantity of membranous partitions stuffed with a sort of pulp and 

 radiating in a confused manner; while a vertical section showed a 



* Comptes Rendus, xcii. (1881) pp. 421-4. 



t Bull. Mus. Coiap. Zool. Camb., viii. (1881) pp. 117-25 (2 pis.). 



