542 SUMMARY OF CURRENT RESEARCHES RELATING TO 



division to small sexual colonies, which arise in exactly the same way 

 as the ordinary colonies which are merely formed by parthenogenetic 

 reproduction. These small sexual colonies finally break up into the 

 separate cell-individuals, which then copulate by pairs and form a 

 resting zygote ; a difference between the sexes of the separate 

 individuals is not, or is only slightly, demonstrable. In the closely 

 allied genera Eudorina and Volvox the facts are very different ; in 

 the former there appear at certain times colonies, which can be dis- 

 tinguished as male and female, some produce nothing but ova, others 

 as distinctly give rise, after repeated division, to spermatozoa, which 

 copulate with and fertilize the female colonies. In Volvox it seems 

 possible to homologize the male and female colonies, and indeed we 

 cannot here correctly speak of colonies, but ought rather to regard 

 what are so called as multicellular individuals of the simplest kind, 

 and we have in it the best marked intermediate stage towards the 

 sexual reproduction of the Metazoa. 



If we bear these facts in mind it is not difficult to suppose that 

 the separation of a few small cells indicates the formation of a 

 multicellular colony of " gametes " corresponding to the bundle of 

 spermatozoa. 



As to the physiological significance of the directive corpuscle we 

 have to decide between the views of the author that we have here to 

 do with an elimination of certain nuclear constituents of the egg-cell, 

 and that of Minot, that it is an elimination of the male element. 

 Against the latter we have the fact that in the simpler cases of 

 sexual reproduction in plants, as the algae, there is no process of 

 elimination, such as is required by the hypothesis, and also the fact 

 that it cannot be brought into accord with the known phenomena of 

 parthenogenesis. 



In a note the author states that the recent observations of Fol, 

 Sabatier and others, only came to his knowledge after his essay was 

 completed, and he has not yet had the opportunity to bring them into 

 accord with his own views. He takes occasion, however, to refer to 

 some observations lately made by his assistant. Dr. Blochmann, who 

 has discovered a very remarkable mode of cell-multiplication in the 

 ovarian ova of ants; these have certainly nothing to do with the 

 formation of the cells of the follicle, for the ovum was already 

 surrounded by a chorion, before the numerous small nuclei, which 

 appear in an altogether unexplained way, had become developed. The 

 observations of Blochmann on ants are possibly to be brought into 

 association with phenomena observed in the ova of Myriopods and 

 Tunicates. 



Morphology of the Pineal Gland.* — F. Ahlborn has a short 

 essay on the significance of the pineal gland, a subject which is of 

 especial interest to English students on account of the recent hypo- 

 thesis of Sir Eichard Owen, The author comes to the conclusion that 

 the pineal gland of vertebrates is to be regarded as the rudiment of 

 an unpaired optic rudiment, and he bases this conclusion on the 



* ZeitBchr. f. Wiss. Zool., xl. (1884) pp. 331-7 (1 fig.). 



