234 SUMMARY OF CURRENT RESEARCHES RELATING TO 



contraction of its musculature) is open ; there is no obstacle to the 

 free passage of fluid backwards and forwards. The retraction of the 

 tontacle is effected by the contraction of the wholo longitudinal muscu- 

 lature ; and the tentacles are then so bent that the valve becomes closed. 



The author's account of the central nervous system does not agree 

 in all points with that of Haniann ; he denies the justice of the opinion 

 that the peripheral cells are not nervous, and, though allowing the 

 impossibility of at present making a definite judgment, he is inclined 

 to think that they are nervous, and not merely supporting. 



With regard to the vesicles of Baur, Dr. Scmon objects to the view 

 that they are merely larval organs with no function in the adult, and 

 urges that they increase in size with the growth of the individual. In 

 their morphological characters they agree with the auditory organs of 

 all other animals than insects. Each organ is a saccule or vesicle 

 formed by an ectodermal invagination, in the fluid contents of which 

 there are more or less freely moving bodies. 



The remarkable ciliated funnels of the ccelom, which were described 

 by Johannes Midler, have been but little investigated since 1852 to any 

 good purpose. In structure the true ciliated organ is very simple, 

 consisting of a curved plate provided at its margin with a projecting 

 ridge ; this last is really nothing else than the margin of the plate 

 which has been bent over ; like the plate it consists of long, rather thin 

 cylindrical cells, the elongated nuclei of which are proportionately very 

 large. Each cell appears to carry only one very long cilium, but on 

 this point it is impossible to be confident. The long axes of all the 

 cells are directed towards the centre of the funnel, and this gives rise 

 to very different appearances with different focal points. The organ 

 does not seem to be a real funnel which passes into a closed tube, for 

 the infundibular portion leads into a curved groove open on one side. 

 This groove opens into the sac of the peritoneal membrane, which 

 invests the outer side of the organ, and is continuous with the stalk. 

 This investment consists of flat spindle-shaped cells, each with an 

 elongated nucleus. The muscular fibres of the peritoneum are not 

 continued into the stalk, nor could the author find there any nerve- 

 fibres. The stalk is not hollow, and does not inclose any canal. 

 Though there is no true lumen there are a large number of cells in the 

 clefts in the stalk, which completely resemble the cells which are 

 found in the fluid contents of the ccelom. These are the bodies which 

 Semper called mucous cells, and Hamann, more appropriately, plasmatic 

 wandering cells. They are distinguished from the so-called blood-cells 

 by the very distinct granulation of their protoplasm, that of the blood- 

 cells being clear and not granulated. The suggestion is made that the 

 ciliated funnels have the function of taking up the lymphoid cells which 

 swim about freely in the ccelom, and conveying them to the tissues ; at 

 the orifice of the funnel there are often masses of cells. Dr. Semon 

 does not think that the ciliated funnels are true excretory organs. 

 When the stalk is attached to the peritoneum its tissue is continuous 

 with that of the peritoneal epithelium. The author is of opinion that 

 we may regard the funnels as large and complicated lymph-stoniata of 

 the ccelom, and suggests that the cells have wandered from the enteric 

 blood-vessels into that cavity. A direct connection between this vascu- 

 lar system and the ccelom has not been made out, and it may be that its 

 place is taken by the wandering of lymph-cells through the tissue. 



