SEMEN. 



475 



Of this by far the greatest part is occupied 

 by the filiform tail. For the anterior body 

 there hardly remains more than -^"'to -ifa'". 

 The body is rather flattened on the sides, so 

 as to represent the shape of an almond. 

 Viewing it from the surface (fig. 323. A), it 

 looks like an oval disc, the longitudinal dia- 

 meter of which exceeds the greatest width by 



Fig. 323. 



A B 



Spermatozoa of Man. 

 A, viewed on the surface ; B, viewed edgeways. 



about one half, and which extends itself to- 

 wards the posterior part into the filiform caudal 

 appendix. The anterior extremity of the 

 body is usually rather pointed, almost like the 

 lower part of a pear or the point of an egg. 

 If the body is situated on its edge (Jig. 323. B), 

 it resembles a short rod, rather pointed 

 towards the anterior part, the transverse dia- 

 meter of which measures about from one half to 

 one third of the greatest transverse diameter 

 of the lateral surface. The tail is cylindrical, 

 thin at the posterior part, and prolonged into 

 a very fine point, which can only be perceived 

 by the application of the highest magnifying 

 power. At its anterior part, on the other 

 hand, the double outline can distinctly be 

 traced. But the thickness even here is always 

 less than the thickness of the body. 



MAMMALIA. The spermatozoa of the Mam- 

 malia have quite a similar form, but frequently 

 a more considerable size. The genus Mus, the 

 smallest mammals, remarkable to state, are 

 distinguished in the latter respect. The length 

 in Mus decumanus amounts to T V'"> in Mus 

 musculus T,V"> in Hypudacus arvalis, Sciurus, 

 Talpa T-V"' U1 Plecotus auritus, Cercopithecus 

 ruber -g^/''. In many other cases, in Canis, 

 Felis, Erinaceus, Lepus, Cervus, &c., the 

 length of the seminal fibres is about the same 

 as in man. But even then the body is gene- 

 rally of a considerable size; as, for instance, 

 in Sciurus, Cervus, and Lepus, where it mea- 

 sures -^'", as also in Talpa. The size of 

 the body in a rat amounts even to -^T/". 

 The difference, however, is frequently less 

 considerable. In Canis, Rhinolophus, Hy- 

 pudacus, Mus musculus, &c., the body only 

 measures -y^-^'", and even still less in the 

 horse and cat. 



The form of the body varies extremely*; 

 all, however, exhibit parts corresponding to 

 those of the spermatozoa of man. The fun- 

 damental form likewise is always that of a 



* Tid. R. Wagner's Icon. Pliysiolog. Table I. 

 Elements of Physiology, p. 13. 



flattened oval. The spermatozoa of the mon- 

 key tribe are very similar to those of man ; 

 likewise those ot the cat, in which the body 

 has a similar inverted oval shape ; as also 

 those of the hedgehog. The body of the 

 spermatozoa in the mole, as also in the horse, 

 is uniformly rounded off at both extremi- 

 ties. In the Rhinolophus it presents the 

 same regular form, but at its anterior ex- 

 tremity it seems to be furnished with a short 

 and thin appendix, resembling a point. In 

 other mammalia the posterior extremity of 

 the body, which is in connexion with the 

 tail, is the narrower one, whilst the free an- 

 terior end appears to be rounded off, or even 

 to be more or less flattened. If the an- 

 terior extremity decreases gradually, the body 

 assumes the usual egg form (Cervus, Lepus), 

 whilst it exhibits more the shape of a pear 

 in cases where that extremity is rounded off 

 (Canis, Sciurus). 



The width of the body, as well as the la- 

 teral flattening off, likewise increases with the 

 enlargement of the longitudinal diameter. Its 

 extreme developement is reached, as it seems, 

 in Sciurus (Jig. 321.). Here the body is very 



Fig. 324. 



/Spermatozoa of the Squirrel (Sciurus vulgar is). 

 Viewed in different aspects. 



expanded and thin, like a fine, transparent leaf. 

 The lateral surfaces are hollowed out, like a 

 spoon, or shovel. The margins, or edges, 

 however, do not participate in this. They 

 appear, especially at the anterior end, much 

 thickened. 



Another very remarkable form is seen in the 

 body of the spermatozoa of the Muridye. It 

 is attached to the anterior end of the caudal ap- 

 pendix, like the blade of a knife, but in such a 

 manner that the tail, when viewing the body 

 on the surface, is not situated as usual in the 

 central longitudinal axis of the body, but 

 passes over into one of the lateral margins. 

 It might almost give rise to the conjecture 

 that the one lateral half of the body had 

 arrived at its full developement, whilst the 

 other had dwindled away and been lost. In 

 fact, the whole appearance of the body seems 

 to justify the assumption of such a non-sym- 

 metrical kind of developement. At the point 

 which usually corresponds to the centre of the 

 body, the lateral part, distinguished by its 

 thickness, is prolonged into the tail. The 

 thickness gradually decreases towards the 

 upper extremity, which is bent in an arched 

 manner, presenting a convexity towards that 



