324 The Spermatozoa of Allolobophora Foetida 



second polar bod_y, and it is an interesting fact that several investigators 

 have observed the division of this centrosome in other eggs. 



If, on the contrary, we attribute to these three spermatic structures 

 the value only of basal corpuscles, we still do not escape the centrosome 

 problem, for Lenhossek (9), and Henneguy (G), claim that the basal 

 corpuscles of cilia have their origin in the centrosome. 



If they are indeed centrosomes, we must follow their logical implica- 

 tion and admit that they can be placed in evidence for the theory that 

 the centrosome has its stage of activity and its stage of rest, the former 

 represented by the aster, the latter by the so-called naked centrosome. 

 The stage of activity of the spine and middle-piece centrosomes — 

 assuming they are such — has but an ephemeral expression in the egg. 

 and it seems only logical to assume that after this period of activity 

 they may return again to a resting stage. With more exact technical 

 methods, it may be possible to trace them in the egg during the rest- 

 ing stage and this can be assumed also for the egg centrosome. We 

 wish to accentuate these points, as the egg of Allolobopliora has hereto- 

 fore given evidence only, in favor of the theory that the centrosomes 

 arise de novo, and are " the expression rather than the cause of cell 

 activity " (4). 



This evidence, in brief, is as follows: The complete disappearance of 

 both male and egg attraction-spheres at a definite stage of the egg's 

 development. A lack of decisive evidence that the rays of the male 

 aster focus at any one point in the middle-piece (5), or that the rays 

 of the cone focus at the base of the spine. Further, an inconstancy in 

 both size and form of the egg centrosome at a given stage of the devel- 

 opment of the spindle, and a lack of evidence of any division of either 

 egg or sperm aster. 



Although the greater part of this evidence is negative, we have no 

 right to ignore it — we may say rather, that the centrosomes of Allolobo- 

 pliora present conflicting evidence that demands rigid cross-examination. 



BIBLIOGEAPHY, 



1. Ballowitz, Emil. Untersuchungen iiber die Struktur dex* Spermatozoen, 

 zugleicli ein Beitrag ziir Lelire voin feinei'en Bau der kontraktilen Ele- 

 mente. Zeit. f. wiss. Zool., Bd. 50, Hft. Ill, 1890. 



2. FiCK, E. Ueber die Eeifung und Befruchtung des Axolotleies. Zeit. 

 fiir wiss. Zool., Bd. LVI, Hft. IV, 1893. 



3. Field, George Wiltox. On tlie Morphology and Physiology of the 

 Echinoderm Si)erniatozoon. Journ. Morph., Vol. XI, No. 2, 1895. 



4. Foot, Katharine. The Origin of the Cleavage Centrosomes. Jonrn. 

 JMorph., Vol. XII, Xo. 3, 1897. 



