980 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and the third innermost layer consisted of a large number of small 

 round daughter-cells. In a second stage of development observable 

 in mature glands, the nuclei of the daughter-cells were seen con- 

 verted into spermatozoids, the exterior half of the nucleus becoming 

 the head and the other interior half the middle part and tail of the 

 spermatozoon. The protoplasm of the daughter-cells took no part in 

 this transformation, and enveloped the bodies of the spermatozoa, 

 making them cohere into bundles, from which the tails of the 

 spermatozoa projected towards the central canal. These masses of 

 protoplasm enveloping the bodies of the spermatozoa resembled the 

 figures described by the earlier observers as " spermatoblasten." In 

 this stage the above diagrammatic column consisted, from the outside 

 inwards, of the primitive cell, the mother-cell, and the bundle of 

 spermatozoa. In the next stage of development the formation of the 

 spermatozoa, arising always in the same manner from the nucleus of 

 the daughter-cells, was pushed farther outwards, so that the column 

 now consisted of but one large round cell on the outside and bundles 

 of spermatozoa on the inside. The formation of the seminal cor- 

 puscles advanced still farther, and at last the whole column, as far as 

 the wall of the canal, consisted of spermatozoa, the bodies of which 

 were agglutinated into bundles by masses of protoplasm, their tails 

 being directed inwards. Primitive cells out of neighbouring columns 

 now intercalated themselves between the wall of the canal and the 

 spermatozoa, pushing the latter towards the middle. By the develop- 

 ment of the mother- and daughter-cells the spermatozoa were pressed 

 and discharged into the central canal. The process thus described 

 then began anew. 



Dr. Biondi examined this structure of the seminiferous canals, 

 and development of the spermatozoids in the bull, the swine, the cat, 

 the rabbit, the guinea-pig, the rat, and other mammalia ; and in all 

 these cases he had found the same results. 



Wandering Cells in Epithelium.* — The presence of wandering, 

 leucocytes in epithelium, shown by Stohr to be normal in the case of 

 the follicular glands and tonsils, and also observed by Bockendahl in 

 the trachea, has been noted by Dr. J. H. List in three instances where 

 it is apparently constant and normal. (1) In the epithelium of the 

 barbules and upper lip of Cohitis fossilis he observed the abundant 

 occurrence of leucocytes in all the layers from the connective tissue 

 of the corium outwards, even to the surface. They lay sometimes in 

 numbers in small dilated cavities, but were found usually between the 

 epithelial cells, and the thin extended nucleus observed in many of 

 them would seem to be the result of the migration outwards between 

 the cells. (2) In the epithelial layers of the ordinary epidermis of 

 Cohitis fossilis the leucocytes occurred abundantly between the epi- 

 thelial cells or between them and the frequent club-shaped cells. 

 (3) In the cloacal epithelium of Elasmobranchs (^Torpedo marniorata, 

 Maja miraletus, Squatina vulgaris, &c.) List observed the migratory 

 corpuscles from the mucosa, where they were heaped up, through the 



* Arch. f. Mikr. Anat., xxv. (1885) pp. 264-8 (1 pi.). 



