64 8UMMAEY OF CURRENT RESEARCHES RELATING TO 



Koehler's studies give evidence of tlie connection between the 

 "heart" and the blood-vascular system, which, while affirmed by 

 Ludwig, Carpenter, and others, has been denied by Perrier and 

 Apostolides. The organ in question is described as " a reticulum of 

 connective tissue, supporting cellular elements that undergo a peculiar 

 degeneration, the final result of which is the formation of numerous 

 pigment-masses ; " it might, perhaps, be convenient to speak of this 

 body as the " plesiform gland " ; it is most certainly not a heart, and 

 may probably have something to do with the production of the common 

 brown pigment-bodies. 



After noting and criticizing some of Koehler's statements as to the 

 fusion of the two vascular systems and other points in the anatomy of 

 Spatangids, Perrier's recent note on the organization of Crinoids is 

 taken up, and it is pointed out that, for the investigation of certain 

 anatomical points, Antedon eschrichti affords more satisfactory material 

 than A. rosacea. The blindness of the vessels connected with the 

 " ovoid gland " is apparent only, and is due to the study of single thin 

 sections ; on the whole, Mr. Carpenter agrees rather with Ludwig 

 than with Perrier in his views on the vascular system; the latter, 

 however, is the first continental naturalist who has supported publicly 

 the Carpenters' doctrine of the nervous nature of the fibrillar envelope 

 of the chambered organ.* Mr. Carpenter reports the presence of 

 bipolar cells in the branches of the axial cord in Pentacrinus, Bathy- 

 crinus, and A. eschrichti; and, in the last-named he has found that 

 there is in the disk a fibrillar plexus which forms an annular network 

 around the lip. Extensions of this plexus are, in all probability, 

 connected with the fibrils of the sub-epithelial band, which by many 

 anatomists is regarded as the sole nervous apparatus of the Crinoidea. 



Ccelenterata. 



Nervous System of Porpita t — After a short account of the 

 literature of the nervous system in the Ccelenterata, H. W. Conn and 

 H. G. Beyer give a sketch of the general anatomy of Porpita before 

 describing in detail the nervous and sensory structures of the animal. 

 The nervous system consists entirely of scattered ganglion- cells, gene- 

 rally tripolar, but frequently also bipolar and sometimes multipolar ; 

 the fibres may be traced for some distance, dividing and subdividing, 

 until they are finally lost in the muscular layer ; in some cases the pro- 

 cesses of several ganglion-cells unite. Transverse sections show that 

 these cells are invariably ectodermic, and never endodermic as is the 

 case in certain other Ccelenterata ; the nerve-cells are most abundant in 

 those parts of the body, e. g. the velum, where the muscular system is 

 well developed, and appear to be entirely absent from the nutritive 

 zooids which are unprovided with muscles. There is no trace of any 

 central nervous system : no nerve-ring exists such as has been 

 demonstrated in Medus£e. 



* Of. this Journal, iii. (1883) p. 661. 



t Studies Biol. Laboratory Johns Hopkins University, ii. (1883) pp. 433-45 

 (1 pi.). 



