48 CALIFORNIA ACADEMY OF SCIENCES. [3D Ser.. 



centrosomes and other structures in the cell remained dor- 

 mant and separate. 



This connection of the archoplasms in two adjoining cells 

 can, I think, best be explained as a necessary conjugation — 

 a preparation for the final mitosis of the cell. It is well 

 known that such conjugations of nuclei have been observed 

 in infusoria, and it has been proven to be an indispensable 

 rejuvenation of the cell. The conjugation of the archo- 

 plasms is probably a similar necessity — a rejuvenating pro- 

 cess without which, perhaps, a degeneration of the archo- 

 some would ensue. In connection with this I will also call 

 attention to the observations of K. v. Kostanecki and A. 

 Wierzejski ("Ueber das Verhalten d. sog. achromatischen 

 Substanzen," etc.), Arch. f. Mik. Anat., Bd. 47, 1896, Heft. 

 2). These investigators have shown how in the fertilized 

 ovum of Physa the centrosome (archoplasm and centrosome) 

 separates from the sperm nucleus and traverses the egg cell 

 in a very independent way (figs. 3, 9, 12, 13). This 

 shows according to my judgment that in the above case 

 the archosome is to a great extent independent of the nu- 

 cleus; but even a greater proof of the independence of 

 the archosome is found in a most important treatise on the 

 Spermatogese von Paludina vivipara, by Professor Leo- 

 pold Auerbach (Jenaische Zeitschrift, Bd. 30, 1896, Heft. 

 4). This admirable memoir arrived just as I was reading 

 the final proof of the present paper, and time will not per- 

 mit of my making more than a review of the summary of 

 results. Paludina vivipara produces two kinds of sperma- 

 tozoa: one possessing the regular form and structure con- 

 sisting of nucleus and cytoplasm, and probably archosome 

 also; the other kind, which has been known as the worm- 

 like form, contains no nucleus, but is composed principally 

 of cytoplasm. It has the value of a Nebenkern. The 

 chromosomes of the original nucleus are being destroyed or 

 ejected, and the Nebenkern, together with part of the cyto- 

 plasm, develops into an independent spermatozoon. In the 

 figures (i3« to q) of Professor Auerbach, I find nothing 

 which resembles a centrosome or archoplasm, but I think 



