840 SUMMARY OF CURRENT RESEARCHES RELATING TO 



very vascular ; in transverse section the glands are seen to possess 

 an outer layer of granular cells, belonging to the perivisceral cavity ; 

 below this there is a fibrous layer, which sends off trabeculfe into 

 the substance of the gland ; this last has the appearance of a compound 

 tubular gland, " or perhaj^s rattier of a folded membrane ; " the duct 

 opens on to the transverse fold in the intestine. The presence of 

 these highly specialized glands is perhajis to be correlated with the 

 absence of segmental organs. 



After an account of the vascular, the author comes to the nervous 

 system, where he directs attention to the hyaline baud lying on the 

 upper surface of the ventral cord ; in the place of the three ordinary 

 we find here four tubes, three of which follow the general plan ob- 

 served in other Oligochasta, while the fourth, which is about equal in 

 size to either of the two smaller lateral ones, lies beneath the central 

 larger one. 



The study of the generative organs naturally leads to a considera- 

 tion of Perrier's well-known classification of the Oligochfeta ; there 

 is some reason to think that PleurochcBta is intermediate between the 

 intra- and post-clitellian groups ; nor is this the only point in which 

 the French naturalist's classification appears to be artificial — in many 

 points Pleurochceta resembles Penchctta, but has not the two caeca on 

 the alimentary canal nor the double spermathecae, which are invariably 

 found in the latter genus. 



Weighing the advantages and disadvantages of regarding the 

 existing classification of Perrier as not sujSicicntly elastic, or of form- 

 ing a fresh fourth group, the author inclines to the latter course, and 

 proposes to form a group of infra-clitellian forms for the reception of 

 his new genus. 



In a postscript the author refers to a memoir by Vejdovsky which 

 explains the anomalous structure of the dorsal vessel in Pleurochceta, 

 by describing the formation of the heart from two primitively distinct 

 rudiments. 



Anatomy andHistology of Lumbriculus variegatus.* — C. Biilow, 

 in preparing for his investigations, killed Lumhriculi in very weak 

 solutions of osmic acid, by which reagent the cuticle is not separated 

 from the matrix, while the cilia are beautifully preserved. The 

 specimens were carefully hardened by weak chromic acid, and then 

 by alcohol, and coloured by picro- or borax-carmine — or, better, by a 

 mixture of the two. After imbedding in })arafiin, sections were cut, 

 and after the paraffin had been removed by xylol, were put up in 

 Canada balsam. 



After some notes on habits and external characters, we come to an 

 account of the digestive canal ; here several well-marked divisions 

 are to be made out. The short pharynx is protrusible, and its tissues 

 are ciliated. The succeeding portion is divisible into an upper and 

 a lower cavity, separated by two folds which meet but do not touch 

 one another. The cells of the lower cavity are about as long as 

 broad, while those of the upper are elongated. The so-called liver- 



* Zeitschr. f. Wiss. Zool., xxxix. (1S83) pp. G4-90 (1 pi.). 



