728 SUMMARY OF CURRENT RESEARCHES RELATING TO 



propose a more thorougli explanation of the entrance of tlie spermatozoon. 

 The jelly round the egg, swelling in contact with water, presents from 

 the surface inwards more and more dense strata. The spermatozoon^ 

 once attracted to the ovum, tends to penetrate wholly in order to 

 experience the contact over its whole surface, and that as long as it meets 

 strata of increasing density. "When the absorption of water by the jelly 

 is complete, the attraction which the strata of increasing density 

 exercised upon the spermatozoon ceases, and by this time a penetration 

 has probably occurred. M. Massart experimented with various gelatin- 

 ous substances, some of which worked as well as the jelly of the ova 

 themselves. 



Spermatogenesis during* Inanition.* — Dr. V. Grandis has experi- 

 mented with pigeons, and finds that a fast of a few days is sufficient to 

 alter the production of spermatozoa. When fasting it probably happens 

 that there is a cessation of the production of the elements which should 

 be converted into nematosperms, and that those only continue to grow 

 which have already begun to be developed. The new formation of cells 

 which is observed after the twelfth day of inanition is not destined for 

 the production of new nematosperms. During inanition spermatozoa 

 die in the interior of the seminiferous canaKculi. The elements of which 

 the testicle is composed break up when the loss of weight undergone by 

 the fasting animal is more than 40 per cent. ; it is probable that this 

 alteration is effected to maintain the animal alive with the products 

 which result from the reduction of the testicle. The constituent 

 elements of the spermatic canaliculi which resist the effects of fasting 

 are, in decreasing order, the spermatozoa, the elements of the central, 

 and the elements of the median layer. The cells which are preserved 

 longest have the character of those which line the walls of these 

 eaualiculi ; this important fact shows that, although the testicle may be 

 reduced to a third of its primitive dimensions, the elements which are 

 capable of giving rise to all the others are the last to disappear. 



p. Histology.f 



Phenomena of Indirect Nuclear Fission in Investing Epitlielia.| — 

 Dr. O. Barbacci finds that the phenomena of indirect nuclear fission 

 persist completely in all the investing epithelia of the guinea-pig, 

 rabbit, and dog. The intensity with which the regenerative processes 

 are effected varies with the different organs to which the epithelium 

 belongs, with different animals, and with different individuals. Of the 

 three animals examined, the guinea-pig exhibits the most active processes 

 of regeneration ; the other two are much less, although about equally, 

 active. The intensity with which the karyokinetic processes are 

 developed in investing membranes exhibits a complete independence of 

 the morphological characters of the ejiithelia themselves. There does 

 not appear to be any constant relation between the activity with which 

 regeneration is accomplished and tbe degree or quality of the function. 

 Although it cannot be absolutely demonstrated, it is very probable that 

 the phenomenon of indirect nuclear division, in investing epithelia, is not 

 continuous but intermittent, and this less for reasons of space than for 

 those of time. 



* Anh. Ital. Biol., xii. (1889) pp. 215-22. 



t This seel ion is limited to papers relatiug to Cells and Fibres. 



I Arch. Ital. LJiol., xii. (ISbi'J) pp. 184-G. 



