442 SUMMARY OP CUBRENT RESEARCHES RELATING TO 



In the female the openings of oviduct and vagina on each side are 

 quite close together, and surrounded by a common chitinous ring. 



At the end of the memoir a classificatory table is given of the family 

 Cyiheridse for the determination of the genera. 



Vermes. 



Vascular System of Annelids.* — M. M. Jaquet commences by 

 giving an account of the vascular system of various Hirudinea : — 

 Hirudo medicinalis, Aulostoma, Nephelis, Pontobdella verrucosa, and 

 Clepsine; Lumhricus terrestris is the selected type of Oligochsetes ; and 

 the Polychaeta are represented by Arenicola piscatorum, Terebella 

 mecJcelii, Sjpirographis pallanzanii, Protula intestinum, Nephthys scolo- 

 pendroides, Nereis, Siphonostoma diplochaitos, and Hermione Jiystrix. 



This comprehensive survey reveals profound modifications in the 

 vascular system of animals which, according to the author, some zoolo- 

 gists have grouped as Annelids, and is sufficient to justify an expres- 

 sion of opinion as to the relationships of these forms with one another. 

 As is well known, the position of the Hirudinea has been the subject 

 of many controversies ; M. Jaquet concludes that they form a very 

 distinct sub-class of the Chgetopoda ; the lowest grade of the circula- 

 tory system is seen in the Ehynchobdellidae ; if perfection were the 

 result of quantity Hirudo, which has four large canals well developed, 

 •would be the highest, but Pontobdella by the possession of verrucse on 

 its skin, the processes of which play an important part in the act of 

 respiration, and Branchellion with its functional if not morphological 

 gill-processes, urge their claims to this place. It is not the size but 

 the differentiation of a system which marks the systematic position of 

 its possessor ; when there are sinuses the division of labour is least 

 marked, and Clepsine is therefore the lowest of the Hirudinea. In 

 passing his final judgment on the relative positions of Pontobdella 

 and Hirudo the author awards the palm to the latter on the ground 

 that the former appears to have a small sinus at its anterior end. 



The differences between the Polychaeta and the Hirudinea are 

 very marked, the former being without the lateral canals which are 

 found in leeches, and the leeches have no lateral canals of the 

 ganglionic chain such as are found in marine worms. It is easier to 

 institute a comparison between Polycheeta and Oligochseta; if we 

 take Arenicola piscatorum and the earthworm we find that both have a 

 dorsal canal attached to the dorsal surface of the digestive tract 

 and passing anteriorly into the region of the cerebral ganglion ; 

 they both want lateral, but both have neural canals ; Arenicola wants 

 the " hearts " which are found in the earthworm, but has instead a 

 contractile dilatation in the anterior portion of the dorsal vessel. 

 In the earthworm the intestino-tegumentary vessel arises from 

 the dorsal, gives off a number of branches to the oesophagus 

 and pharynx, and irrigates the stomach and the glands of Morren. 

 In Arenicola the expansion which is regarded as the heart, and which 



* MT. Zool. Stat. Neapel, vi. (1885) pp. 297-398 (3 pis.). 



