846 SUMMARY OF CURRENT RESEARCHES RELATING TO 



cords (Cbaetognatlii, Chiton, &c.) ; (4) the diflFuse part is gradually 

 lost, and the cords are retained. These conclusions are confirmed by 

 citations from numerous recent researches. 



On this paper C. S. Minot* says "Dr. Hubrecht has, we think, 

 successfully established two very important generalizations (1) that 

 in the lower animals there prevails a uniform type of nervous tissue, 

 ganglion-cell and nerve-fibre being incompletely diflerentiated, and 

 the nerve-fibres being in the form of a network ; (2) that the nerves 

 were developed by concentration of the diffuse tissue along certain 

 pathways. His paper is certainly one of much value and originality. 

 Systematically the position of Pseudonematon is uncertain, but it 

 probably belongs somewhere near the Nematodes and Plathelminths." 



Anatomy of Cestoda.t — H. Griesbach finds that in the body of 

 Cestoid worms there is only a single kind of connective substance ; 

 this is the gelatinous tissue which is traversed by anastomosing 

 lacunar spaces ; the so-called cuticle, which would be better known 

 as the body-wall or limiting membrane, is not of epithelial or of con- 

 nective character, but is a development from the gelatinous tissue. 

 The structures which have been hitherto known as subcuticular cell- 

 layers do not represent either a matrix or cells of connective tissue, 

 but are formed of living protoplasm, comparable in character and 

 function to the protoplasmic body of certain Protozoa. The water- 

 vascular system consists of two well and two more feebly developed 

 canals which extend through all the strobila ; the former give rise to 

 transverse anastomoses and branches which pass into the lacunar 

 system of the gelatinous tissue, in each proglottid; the latter open 

 into the larger canals. 



The author is of opinion that the lacunar system represents the 

 coelom ; in this we find infundibular structures, which form the com- 

 mencement of the so-called water-vascular system, and are more 

 abundant in the peripheral regions of the body. The fluid contained 

 in the vessels takes a centripetal direction from the funnels, passing 

 by fine tubules, comparable to capillaries and frequently communi- 

 cating with one another ; these open, generally in a deltiform fashion, 

 into the longitudinal canals of the strobila and the looped vessels iu 

 the scolex. Concretions of calcic carbonate, having a kind of pro- 

 tective function, are to be found over the whole body ; these are not 

 calcified cells, but are formed in the water-vascular system, perhaps 

 by the aid of special unicellular glands. At the same time that 

 system retains the function of a renal apparatus. 



The musculature consists essentially of longitudinal, circular, and 

 dorsoveutral muscles ; the nervous system is represented by four 

 ganglia in the scolex, which are connected by commissures, and give 

 off peripheral nerves in the Bothridia. In the strobila wo find, 

 externally to the water-vessels, two nerve-cords, but commissures 

 between these were not to be detected. 



The results of these observations were based on a study of Soleno- 

 pJiorus megaloccphalus. 



* Science, ii. (1883) p. 382. 



t Arch. f. Mikr. Anat., xxii. (1883) pp. 525-84 (3 pis.). 



