. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 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-g-fa"' —3%„'"'), which lie together in round masses ; being generally situated on the circumference of a large central ball among the bri
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 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-g-fa"' —3%„'"'), 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. r> Developement of the spermatozoa in Lumbricus. the Helicinae (fg. 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 ofIio/li/ier-\- on the clevelopement 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 all 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 meantime gradually dissolves. Similar fasciculated groups are likewise
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