458 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the stomach. It is the " seconcl c«soi)hagus " of Otto, but has also 

 been regarded as a glaud, and as a diverticulum of the stomach. 

 Horst's observatious lead him to consider the organ as circulatory. 

 Posteriorly the stomach and gut form blood-sinuses between their 

 muscular and epithelial layers, but in the anterior regions of the body 

 — here, as in Enchytrasidse — the same muscular layer is produced to 

 form a definite blood-vessel. The same arrangement occurs in young 

 Terebella), but in other Annelida is only transitory during the larval 

 period. 



The blood in CliloraemidaB is, as the name denotes, green, but the 

 organ now in question is much darker than the blood. This colour 

 is due to a brown cellular fibrillar mass (as shown by sections), which 

 largely fills up the lumen of the organ posteriorly. This mass may 

 correspond to the " corps cardiaque " of many sedentary Annelida, 

 but is by Horst more particularly compared with the coiled mass of 

 vessels described by Vejdovsky in Enchytroeus appendiculatua as 

 springing from a blood-sinus. 



Segmental Organs of Serpula.* — Mr. W. A. Haswell, opposing 

 Claparede, asserts that the true segmental organs in this animal " are 

 entirely distinct from the so-called tubiparous, and, though of a simple 

 type, are not unlike those of other Annelids. They are pyriform 

 sacs . . . occurring in pairs in all the segments of the abdomen. They 

 open externally on the sides of the segments by slit-like apertures 

 . . . and, presumably, oj^en also into the body-cavity." 



In Eupomatus these organs serve not only as efferent ducts for 

 the generative products, but as seats of development for the ova. 



Origin of the Nervous System of Nematodes.f — Prof. 0. Blitschli 

 finds that the recent works of A. Lang on the nervous system of the 

 Platyhelminths, of Gatfrou on Distomum, and of Joseph on Nematodes 

 give support to some new ideas as to the origin of the nervous system 

 of the round-worms. 



Lang has shown that the nervous system of flat-worms is by no 

 means so simple as has been ordinarily sujiposed, and that there are 

 more than the two longitudinal ventral trunks which are commonly 

 described ; Gaffron has found that from the so-called cerebrum there 

 arises on either side a pair of backwardly directed longitudinal 

 nerves, of which the better developed pair is ventral, and the other 

 dorsal ; just at the point of origin of the pairs there is another 

 posterior longitudinal nerve, which extends along the sides of the 

 body, and may be known as the lateral nerve. These six nerves are 

 connected with one another by transverse commissures ; and at 

 certain points there arc plexiform connections, similar to, though 

 much less numerous than those found by Lang in Turbellarians. 

 Biitschli justly remarks that the arrangements found in the Trematoda 

 seem to lead to the peculiar disposition of the nerve-trunks which is 

 known to obtain in the Nematodes. 



The simple cerebral mass of flat-worms may easily be supposed 



* Zool. Anzeig., viil. (1885) pp. 96-7r 



t Movphol. Jahrb., x. (1885) pp. 486-93 (1 pi.). 



