SEMEN. 



497 



in the Branchiobdella. In the latter, these 

 windings are, however, confined to the anterior 

 half; but they are so close and numerous that 

 they formerly gave rise to the erroneous 

 opinion of one of us*, namely, that the fibres 

 of this part were jointed or articulated. 



These fibres are in all cases produced 

 separately from small cells, containing nuclei 

 (generally of -fa fff ^/"), which lie together 

 in round masses ; being generally situated on 

 the circumference of a large central ball among 

 the bristled worms and Hirudines, as among 

 Fig. 387. 



Developement of the spermatozoa in Lumbricus. 



the Helicinae (jig. 387. A.). According to 

 analogy with the higher animals the sperma- 

 tozoa are also unquestionably produced in an 

 endogenous way, and, as is shown by the ob- 

 servations of Kulliker-\- on the developement of 

 the spermatozoa in Lumbricus and Distoma, 

 in the interior of the nuclei. We cannot, 

 however, trace the process of formation with 

 decisive certainty owing to the smallness of 

 the elements in question. The external ap- 

 pearance (B) leads us, however, to infer that 

 the cellular formations grow out into a long 

 fibre. The cells gradually assume a fusi- 

 form shape, but still remain united toge- 

 ther in one group. It is the peripheric end 

 which seems to get extended in forming the 

 spermatozoa. Wherever a central ball oc- 

 curs, for instance, in Lumbricus and Hirudo, 

 the group of cells at this stage of the deve- 

 lopement presents a very pretty appearance. 

 The spermatic fibres radiate towards alj 

 directions from the central ball, into which 

 their thickened extremity is inserted; they 

 have then made their exit in a still imperfect 

 state (c). They soon, however, get grouped 

 together into bundles, the points of the fibres 

 gradually converging towards one common 

 point (D); the central ball in the mean time 

 gradually dissolves. Similar fasciculated 

 groups are likewise seen in the spermatozoa of 

 Annelids in most cases even where the central 

 ball is wanting in the Trematoda, &c. for in- 

 stance. The same facts we have already noticed 

 when speaking of the Gasteropoda. *We then 

 proved that the separate elements in the groups 

 of cells originate through the continued en- 



* Wagner in Miiller's Archiv. 1835, S. 222. 

 f Kolliker, Die Bildung der Samenfaden, u. s. w. 

 S.37. 



VOL. IV. 



dogenous formation from one single, and at 

 first simple, cell. It is easily traceable that 

 the same takes place in the Annelida, when 

 we compare the different constituents of the 

 semen, for instance, in Lumbricus. Here, 

 as in the Gasteropoda, we meet with nu- 

 merous formations, which in one continued 

 series of transitional developement lead to the 

 form of groups of cells, taking their origin 

 from one single nucleated cell containing some 

 brownish granules. In the interior of this 

 cell numerous daughter cells are produced, 

 the number of which continually increases. 

 Finally the wall of the mother cell bursts, the 

 enclosed cells become free, and deposit them- 

 selves around the remainder of the cellular 

 contents, which latter have not participated in 

 the formation of the daughter cells. 



Whenever the central ball is wanting in the 

 group of cells, the mother cell generally gets 

 destroyed at an earlier period. This view is 

 supported by an observation of Kollikcr, from 

 which it appears that the groups in Spio con- 

 sist at first only of few and large cells, which 

 subsequently increase in number whilst their 

 size decreases. It is impossible, however, to 

 draw a very strict boundary here. Even in 

 the former case the increase of the daughter 

 cells frequently seems to take place after the 

 membrane of the mother cell has been destroyed, 

 which may also be seen in the Helicinoe. In 

 other cases the mother cell not only survives 

 the endogenous formation of daughter cells, 

 but also the process of the developement 

 of the spermatozoa. We are at least led to 

 this inference by the observations which we 

 had the opportunity of making in some 

 small species of Terebellaria from the North 

 Sea, namely, that the bundles of spermatozoa 

 are sometimes still enclosed by one common 

 oval cyst. 



JSryozoa. A similar series of phenomena we 

 Fig. 388. 



Spermatic cells of Flustra carnosa; (A) still con-* 

 tained in the mother cyst ; (B) partially free. 



find in some Bryozoa (which would be perhaps 

 Fig. 389. 



(I 



Developement of the spermatozoa of Flustra carnosa. 

 (After Kolliker.} 



most correctly classed among the Annelida), 

 for instance, in Laguncula and Alcyonella*, 



* Yid. Von Beneden in the Mem. de 1'Acad. de 

 Bmxelles, torn. xv. and xviii. 



K K 



