SEMEN. 



499 



seems rather to indicate a gradual elonga- 

 tion of the cells. The spermatozoa lie to- 

 gether in bundles, either enclosed by the 

 cysts or free. 



AcalephcE and Anthozoa. The Acalephaeand 

 Anthozoa exhibit quite a similar series of phe- 

 nomena. The bodies of the spermatozoa are 

 usually round, frequently however, especially 

 among the Medusa? ( fig. 394.), oblong, cy- 



Fig. 394. 



3 



Spermatozoon of Pelagia denticulata. 



lindroid. Little is as yet known respecting 

 their developement. The spermatozoa have 

 generally a fasciculated style of grouping 

 together, and mostly so at a period when they 

 are still enclosed by cyst-like cells. Pre- 

 vious to the maturity of the generative capa- 

 city, these cysts contain, as has been proved 

 with regard to the Medusae, numerous small 

 vesicles, which subsequently pass through ap- 

 parent prolongation into spermatozoa. 



Infusoria. The Infusoria are especially 

 distinguished by the want of a sexual mode of 

 propagation. There is no trace of either 

 spermatozoa or ova to be discovered in 

 them. Ehrenberg, it is true, describes in these 

 animals particular organs of procreation, both 

 male and female ; but there is no foundation 

 for the assignment of such an import to 

 these particular parts of their structure, it 

 being altogether an arbitrary one. The proof 

 of the existence of spermatozoa and ova 

 the * characteristic structures is indis- 

 pensably necessary to prove the embryo-pre- 

 paring function of certain parts, and to justify 

 their being interpreted as generative organs. 



General conclusions respecting the morphology 

 and developement of the spermatozoa. A re- 

 view of the description now lying before us, of 

 the form and developement of the seminal ele- 

 ments in the several divisions of the animal 

 kingdom, and of the mutual relations of the 

 respective formations, must unavoidably lead 

 us to claim for them a different morphological 

 value. 



By far the greater part of the spermatozoa, 

 all the so-called seminal fibres, which are 

 distinguished by the linear form of the body, 

 are produced in an endogenous way, and that 

 (with the exception of the spermatozoa in 

 the Decapoda) separately in the interior of 

 vesicular elements. KolKker* was the first 

 who directed attention to the wide exten- 

 sion of this mode of production f , hav- 



* Die Bildung der Sainenfaden. 

 t The doubts which Keichert recently raised 

 against the correctness of the statements aud obser- 



ing claimed it likewise for such animals, in 

 which appearances are rather in favour of an 

 immediate metamorphosis of the vesicles of 

 developement into seminal fibres (by means of 

 elongation, growing out, &c.). The laws of 

 analogy certainly justify us in drawing the 

 same inference as Kollikcr ; the more so, as 

 observation has proved that many animals, 

 the developement of whose spermatozoa was 

 formerly accounted for by the latter me- 

 thods, evidently also follow the endogenous 

 type. 



It is difficult to trace the intimate develope- 

 ment of the spermatozoa in the interior of 

 these vesicles ; but it appears probable that it is 

 brought about by the junction of molecular 

 corpuscles, which join each other linearly, and 

 which have been deposited from the con- 

 tents of the vesicles. Indeed, such a mode 

 of procedure does not seem to be at all sin- 

 gular in the history of developement of organic 

 tissues. By saying this, we do not exactly 

 mean to allude to the mode of formation of 

 the muscular fibrils in the interior of the 

 sarcolemma of a so-called primitive fasciculus, 

 since at present we know too little about 

 it ; yet, we cannot help reminding our readers 

 of the process of lignification in the vegetable 

 world, or of the production of the so-called 

 spiral vessels, which essentially seem to be 

 founded on a perfectly analogous deposit of 

 a firm substance, from that which was at first 

 fluid. 



The decision of the question respecting the 

 histological significance of the vesicles of de- 

 velopement is much more difficult. In many 

 cases, especially when they are situated sepa- 

 rately or in small numbers in the interior of 

 the spermatic cells, they have evidently the 

 value of nuclei. Whether this however is 

 always and every where the case, as Kollikcr 

 supposes, we would not assert ; the less so 

 because the appearance and the vesicular 

 form of these structures do not by any means 

 enable us to distinguish them properly from 

 cells void of nuclei. 



By the laws of analogy, we are, however, 

 perhaps justified in forming a judgment on 

 the nature of the respective elements even in 

 such doubtful cases. We ourselves might 

 perhaps even venture to pronounce that the 

 vesicles of developement of the spermatozoa 

 are in all cases nuclei. The unity in the 

 mode of developement of the spermatozoa 

 which would thus be established is certainly 

 very attractive; but we dare not conceal it from 

 ourselves that this inference from analogy 

 is the less to be depended upon, since the 

 genesis of the spermatozoa in the Decapoda 

 furnishes us with a proof that the formation 

 of these elements may also take place J ime- 

 diately in the interior of cells, with' .. the 

 nuclei at all participating in it. vV r e are 

 confirmed in this opinion from the circum- 

 stance that in many Decapoda, for instance in 

 Mysis, it is not the cell itself in which the 

 spermatozoa are produced. The cylindrical 



rations of Kiilliker we certainly must consider as 

 entirely unfounded. 



K K 2 



