ZOOLOGY AND BOTANY, MICBOSCOPY, ETC. 91 



the body in a wide membranous expansion bearing four branchial processes. 

 This last is highly contractile, owing to the presence of numerous stellate 

 muscle-cells between the respiratory and epidermal walls ; the blood- 

 vessels are here also much modified, the abdominal vessel dividing at its 

 termination into two branches, which run round the area, giving off one 

 looped branch to each branchial process, and also branches which cross the 

 area obliquely. There are never more than four processes arising from 

 the floor of the area, but there may be also two smaller marginal pro- 

 cesses. Eight species are enumerated, and the characters of their respiratory 

 processes distinguished and indicated. 



Budding in Oligochaeta.* — Prof. A. G. Bourne finds that there are 

 variations in the mode of budding in different genera and species of 

 Oligochseta. He has made an exact study of Nais (Stylaria) prohoscidea, 

 and finds that when budding is about to commence there is a slight 

 thickening of one of the septa which separate the coelomic segments. This 

 thickening increases, the body-wall in the region thickens, and an actual 

 budding region is formed. This new region elongates and presents a solid 

 appearance. The alimentary canal grows and is at first distinguished by 

 its lighter colour. The budding region divides into two; the anterior 

 portion developes numerous setae, and gives rise to an indefinite number 

 of segments which form the tail of the old worm ; the posterior portion 

 developes four pairs of ventral setae. The characteristic proboscis being 

 developed, the two individuals separate. The budding region usually 

 appears between the twenty-fifth and twenty-sixth segments, so that the 

 twenty-sixth segment of the parent becomes the fifth segment of the 

 daughter, the four anterior segments never presenting dorsal setse, and 

 being in all individuals modified (or cephalized). 



Excretory and Generative Organs of Priapulidse.f — Dr. H. Schauins- 

 land describes the as yet unknown excretory or generative organs of the 

 Priapulidse. The tubes that open with the anus are primitively the efferent 

 parts of the excretory organ, and they only secondarily take on a genera- 

 tive function. From these tubes small canals extend into the ccelom ; these 

 soon branch and form the excretory apparatus. The terminal organs or 

 true secreting parts consist of small pyriform cells, each of which has one 

 extremely long flagellum which projects into the excretory canaliculus, and 

 keeps up an active motion ; in its region the canaliculi are non-ciliated, 

 but on the rest of their course the cells that line them have a few short 

 cilia. The excretory cells may be compared with those of Platyhelminthes. 

 When the production of ova and sperm commences the two tubes begin first 

 to form small folds, which grow into the attaching mesentery ; from these 

 there arise small tubes which in the female are generally unbranched, but 

 in the male are a good deal ramified. 



The generative products are developed from the epithelium of these 

 tubes ; the young cells, as soon as they are larger than the other epithelial 

 cells, appear on the outer surface of the tube ; as soon as they are mature 

 they gradually return, and fall free into the lumen. The spermatozoa have 

 an altogether similar history ; they are at first distinguished from the 

 neighbouring cells by the size of their nuclei. These products pass from 

 the lumen directly to the exterior, and do not, therefore, as in other 

 Gephyrea, first fall into the coelom. In old animals the structure of the 

 gonads is very complicated, owing to the conversion of the tubes into whai 

 look like flat lamellaB. The structure of the excretory organs and tJle 



* Rep. Brit. Assoc. Adv. Sci. for 1885 (1886) pp. 1096-7. 

 t Zool. Anzeig., ix. (1886; pp. 574-7. 



