-808 SUMMARY OF CURRENT RESEARCHES RELATING TO 



origin from the suboesophageal fibrous band. The intermediate nerve 

 is probably the prolongation, in the ventral chain of the appendages, 

 of the great sympathetic. 



The circulatory apparatus is on various types, and between these 

 there are intermediate stages : A. A dorso- ventral circulatory system 

 identical with that found in most Annelids, and co-existing with, but 

 not in communication with, the general body-cavity ; J5. A dorso- 

 vtntral circulatory system in direct communication with the coelom, 

 represented by the system of lateral vessels ; the development of the 

 varicose plexus in the hinder region of the body (Nephelis) tends to 

 make the communication between the two systems less direct ; C. A 

 dorso-ventral system communicating very vaguely with the system of 

 the lateral vessels, and having the varicose plexus so largely developed 

 as to tend to separate the two systems. 



The nephridia undergo modifications which are intimately associ- 

 ated with those of the circulatory apparatus ; in case A they consist 

 of simple tubes which put the coelom into communication with the 

 exterior ; in B the tube of epiblastic origin is associated with the 

 " cupules rouges " or annexes of the system of lateral vessels ; in C 

 the segmental organs have no direct relation to the lateral vessels, their 

 glandular tissue being penetrated by capillaries. 



In the digestive tract a region behind the stomach is of a differ- 

 ent histological structure, and is to be considered as the chief seat of 

 the chemical changes. The Hirudinea eliminate yellowish-brown 

 spherules under the form of pigmentary granulations ; this the author 

 calls the pigmentary function. 



The genital organs of different species may be compared, and it is 

 possible to follow those combinations of the constituent parts which 

 produce different appearances. The glands attached to the recepta- 

 culum penis of the leech have unknown functions ; in the ovaries it is 

 possible to distinguish the germigenous and vitellogenous portions ; 

 the ova may arise directly from the walls of the ovary or on buds ; a 

 mass of egg-cells and a fused mass of vitelline cells may become isolated 

 and have the appearance of a spermatophore. The spermatozoa seem 

 to be developed in essentially the same way as in those animals in 

 which their genesis has been investigated. 



Development of the Head of Polygordius.* — Dr. B. Hatschek 

 finds that the lateral nerves in the head of Polygordius extend into the 

 postoral region and are identical with the oesophageal commissure ; 

 this, therefore, is developed before the rudiment of the ventral medulla 

 becomes apparent. The fibrils which belong to the ventral longi- 

 tudinal muscular band of the head appear before the cephalic vesicle 

 has attained its highest development, and at the same time as that of 

 the first appearance of muscular fibrils in the trunk. From the 

 former a delicate fibril extends into the head ; it lies close to the 

 ectoderm and alongside the outer margin of the delicate oesophageal 

 commissure ; later on, fresh fibrils are added on, and the whole be- 

 comes broader and longer. The dorsal longitudinal muscular bundles 



* Arbeit. Zool.-Zoot. Inst. Wien, vi. (1885) pp. 109-120 (1 pi.). 



