494 



SEMEN. 



at regular intervals, which give to the corpus- 

 cle sometimes an angular appearance, as in 

 Pisa. The length of the rays holds an in- 

 verse ratio to the size of the cells, and is, in 

 most cases, either equal to, or double, their 

 diameter. 



The peculiar form of these seminal ele- 

 ments naturally provokes the question, whe- 

 ther they really represent the developed 

 spermatozoa, or whether they are not per- 

 haps mere phases of developement. The 

 relation in which they stand to the simple 

 spermatic cells suggests a conjecture of 

 this kind ; and the more so as the rays at- 

 tached to them already present the greatest 

 similarity with the usual filiform sperma- 

 tozoa. We regret to say, that we are not 

 yet in a position to decide this question 

 with perfect certainty. From various obser- 

 vations, however, the latter assumption gains 

 in probability. Kollikcr has observed (in 

 Calappa) that the adhering nucleus is lost at a 

 later period ; further, that in Portunus corru- 

 gatus, the cell membrane gradually gets very 

 much contracted ; whilst, on the other hand, 

 the rays considerably lengthen themselves. If 

 we consider, in addition to this, that radiated 

 cells are found in Ilia Nucleus, which (j%-.380.) 



Fig. 380. 



A cell with rays from Ilia Nucleus. (After Kolliker. ~) 



possess extraordinarily long fibres on a very 

 small body ; that finally in Pagurus, as it 

 seems, the rays perfectly sever themselves 

 from the corpuscles ; that, at all events, 

 developed radiating cells, without rays, are 

 often found in the latter, it must induce 

 us to share Kollikcr s opinion, that the ra- 

 diating cells, at this stage of their formation, 

 are not yet perfected ; but that they are more 

 likely to be instrumental in the developement 

 of ordinary spermatozoa. Such spermatozoa, 

 however (if we except the genus Mysis, 

 which is certainly unjustly divided from the 

 Decapoda), have not yet been proved to 

 exist in any of the animals belonging to this 

 class. Kolliker has succeeded only in Dronia 

 Humphii in discovering a great number of fine 

 pale fibres of T ^ /// in the lowest part of the 

 vas deferens, which probably owe their 

 origin to the rays of the seminal corpuscles, 

 which, however, are much shorter than those 

 fibres, hardly measuring above T2\n/"' 



Such a negative result can, however, the less 

 determine our judgment on the nature of the 

 radiating cells, since the observations, which 

 one of us (R. Leuclcarl, together with Dr. 

 Frey) has instituted, with regard to the deve- 

 lopement of the spermatozoa in Mysis, have 

 brought the question pretty nearly to a deci- 

 sion. V. Siebold was already acquainted with 

 the filiform spermatozoa in this crawfish, which 

 are distinguished by their great length (of i'"). 



This animal possesses the more interest for 



us, owing to the remarkable mode of form- 

 ation of the spermatozoa, which is extremely 

 similar to the developement of the radiating 

 cells in the other Decapods. 



The primitive seminal cells in Mysis appear 

 as round pale nucleated vesicles of about - r io /// 

 in diameter (fig. 381.). In the course oftheir 



Fig. 381. 



Developement of the seminal corpuscles in Mysis. 

 (After Frey and Leuckart.) 



further developement, a small wart-like pro- 

 cess (B) rises somewhere on this vesicle, 

 which gradually lengthens itself (c, D), and 

 grows into a long cylindrical tube of -J^'". 

 The nucleus does not participate, in any way, 

 in this metamorphosis. It retains its original 

 form, and remains at its original place in the 

 interior of the seminal cell, which is seated on 

 the cylindrical stafflike a globular appendix. 



In spite of their rather peculiar shape, we 

 do not hesitate to pronounce these seminal 

 elements of Mysis as parallels of the radiating 

 cells of the other Decapods. Excepting the 

 rays, we can find no material difference between 

 them. That the wall of the cell is not immedi- 

 ately metamorphosed into the cylindrical body, 

 is equally as little material as the circumstance 

 that the nucleus remains without change, and 

 does not project outwards. Indeed, we also 

 find the same relation in the radiating cells 

 of Astacus marinus (fig. 382.), where the nu- 

 cleus likewise remains in the interior of the 

 cylindrical radiated corpuscle. 



To judge from their form, these seminal cor- 

 puscles would have most resemblance to the 

 radiated ceils of Pagurus ; but, according to 

 Kolliker' s observations, it would appear that 

 the long cylindrical appendix has originated 



Fig. 382. 



Radiatinq cells of Astacus marinus (After Kolliker.) 



from the metamorphosis of the cellular 

 nucleus. 



The nucleus in Mysis, together with the 

 sorrounding head-shaped part of the seminal 

 corpuscle, is subsequently destroyed, the same 

 as Kolliker has found it in Calappa. There 

 merely remains, then, a simple long cylinder 

 (fig. 383. A), which represents the radiating 

 corpuscle. The formation of the spermatozoa 

 takes place in the interior of this cylinder : 

 they consist of long linear fibres, which lie in 



