48 SUMMARY OF CURRENT RESEARCHES RELATING TO 



generative glands formed ridges of connective-tissue fibres which did 

 not form rounded bodies, but widely open grooves which extended 

 between the muscles ; on the inner face there is again a layer of 

 mother-cells, which give rise to egg-cells. The male organs were 

 only once observed, when they were seen to present all the essential 

 characters of the female. 



Anatomy and Histology of Sipunculus nudus.* — Dr. J. Andrew 

 here gives a full account of his investigations, the preliminary 

 notice of which we have already noted .f With regard to its external 

 form, he points out that, owing to its rich supply of muscles, the 

 integument is highly contractile and that consequently the creature 

 can and does, take on the most various forms. The cuticle is 

 thin, transparent, and so arranged as to be iridescent during life ; 

 the pores of the glands are irregularly distributed over the whole 

 of the body, and vary in size according to the size of their glands. 

 The pigment-spheres have been but rarely noticed, although they are 

 widely distributed over the body ; varying much in dimension, they 

 are seen in sections to be provided with a doubly contoured covering, 

 within which there is a brown granular mass, containing a number of 

 elongated oval nuclei. The circular musculature of the body does 

 not consist of a continuous layer, but of a number of iiattened broad 

 bands, the space between which altogether disappears when the animal 

 contracts in diameter. In addition to these and the longitudinal 

 muscles there is a much more delicate layer of diagonal fibres, more 

 widely separated from one another. The walls of the tentacles are a 

 direct continuation of the proboscis, and within there is a cavity 

 connected with the circumpharyngeal vessel. The value of the in- 

 tegumentary cavities as the seats of respiratory activity is insisted 

 upon, as is the fact that the ventral cord, unlike that of Annelids, is 

 sino'le and not double ; the cord, further, presents no ganglionic 

 swellings except at its termination, though, owing to its form, there 

 would, on superficial examination, appear to be such. The supra- 

 oesophageal ganglionic mass is biscuit-shaped, and presents distinct 

 indications of having been originally double ; like the ventral cord, it 

 is traversed by a network of connective-tissue fibres, and the ganglia 

 are most largely present on the ventral surface of the two spheres, on 

 the anterior margin of the projection, and at the tip of the finger- 

 shaped processes which are given off from it. 



The author is of opinion that the group of the Gephyrea is a 

 natural one, that it stands closest to the Annulata, and that it is 

 justifiably divisible into the two orders of the Sipunculida and 

 Echiurida. 



Sternaspis4 — In this elaborate monograph the structure and 

 development of this Gephyrean is very fully treated by Dr. F. 

 Vejdovsky. He distinguishes a fore- and a hind-body, and recog- 

 nizes seven segments in the former and a varying number in the 



* Zeitschr. f. wiss. Zool., xxxvi. (1881) pp. 201-58 (2 pis.). 



t See this Journal, i. (1881) p. 892. 



X Wien. Denkschr., xliii. (1881) pp. 33-90 (10 pis.). 



