PROBOSCIS. 57 



perfect stylets, yet no trace of a developing spike ; in the other there were three completely 

 formed stylets, yet each varied in length ; while the long spike without a head was fully as long 

 as the largest in that sac — head included. Those in the outer cavity were quite as large as the 

 central stylet. In Tetrastemma Candida I have observed, besides the ordinary stylets, a group 

 of minute crystalline spines, which had no connection with the clear vesicle of the sac. Thus, 

 at present, though I have very often seen these organs inside, and connected with the fluid vesicles, 

 I cannot altogether support Max Schultze's notion that they must be developed therein ; and 

 this would not signify much, since the entire cavity must act as a secreting chamber, else the 

 large ones could receive no increase after they had outgrown the capacities of the globules. 

 M. Claparede stated, in his ' Recherches/ that he had never seen spikes inside those vesicles, but 

 in his subsequent ' Beobachtungen' he figured a developing stylet in a globule in ProsorhocJimus 

 Claparedii. 



In a specimen that had often been under the microscope, I found on one occasion a pair of 

 stylets, apparently from the marginal sac of one side (though this is by no means certain), advanced 

 nearly to the ganglionic portion of the proboscis. One marginal pouch was at any rate empty, 

 while the other retained its three stylets. The free stylets moved very slowly forward, scarcely 

 any progress being made during an hour's observation. At this time the empty sac contained 

 numerous granules, but no circular or ovoid vesicle. Twenty-four hours after the stylets had 

 disappeared. The sac is now observed to be much less than its fellow of the opposite side, and 

 somewhat shrivelled and undefined ; but it contains a small ovoid vesicle, which is traversed by a 

 minute slender spike, whose long diameter exceeds that of the globule, and therefore it cannot be 

 supposed to be within it. In addition there is a free spike, about a third the length of the 

 former. The larger has assumed the shape of a stylet without a head ; the latter is as yet nearly 

 cylindrical (Plate XII, fig. 3). Whatever the function of these organs in the marginal sacs may be, 

 there can be no doubt they have nothing to do with the supply of the central apparatus, for that 

 furnishes its own stylet. 



b. Ejaculatory Duct. 



Through the same region the ejaculatory duct (n) passes to the point where it opens 

 into the muscular space behind the constrictor of the central aperture in the floor of the 

 anterior chamber. The opening (/) of the duct is generally obscured by the apparatus of the 

 central stylet, unless the observer sees it at the moment of contraction of the powerful muscular 

 walls of the reservoir, when the mucous or villous lining is driven forward so as to render the 

 channel more apparent, and a vigorous jet of the minutely granular fluid is propelled into the 

 muscular sac, and then through the stylet-aperture into the floor of the anterior chamber. Closer 

 observation, even when such convulsive contractions are absent, occasionally shows the molecular 

 fluid passing onwards to the anterior chamber; and if the ejaculatory duct is not obscured by 

 the glands, the moving granules of this peculiar fluid are seen therein. Moreover, when the 

 large compound cells (Plate X, fig. 17) have been detached underpressure, and squeezed forward 

 into the reservoir and along the duct, the calibre of the opening into the muscular sac may be 

 ascertained with tolerable accuracy, and is so small that only a single cell at a time can be trans- 

 mitted. The duct has a bent-conical form, a shape that avoids interference with the basal apparatus 

 of the stylet, which occupies the centre of the region ; and its posterior end (that opening into 



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