608 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Spermatogenesis of Lepidosiren.* — W. E. Agar went to the swamps 

 of i In' Paraguayan Chaco to obtain material for studying the spermato- 

 genesis of Lppidosiren paradoxa — a form in which the nuclei attain a very 

 large size and the chromosomes are beautifully clear. He has paid par- 

 ticular attention to the processes of reduction. The somatic number of 

 chromosomes is thirty-eight, one pair conspicuously larger than the rest. 

 In the spermatogonial and also in the somatic nuclei the chromosomes 

 are arranged in a definite plan, the smaller and larger ones being grouped 

 together. Within the main group there is also evidence of a tendency 

 for chromosomes of equal size to be next each other. 



The reduced number of chromosomes in the bouquet stage appears 

 to be arrived at by a parallel conjugation in the early prophase according 

 to Von Winiwarter's scheme. The first maturation division separates 

 entire " homologous " chromosomes. There is no resting stage between 

 the two divisions. In the second division the chromosomes divide longi- 

 tudinally, forming " tetrads," etc., very like those of the first metaphase. 

 We cannot, however, do more than direct attention to this important, but 

 necessarily very technical paper. 



Nature of Seminal Fluid in Man.f — CI. Broesike finds that there 

 is first of all, in erection, a secretion into the urethra of the products of 

 Cowper's glands, and perhaps of urethral glands. There are, then, three 

 acts in ejaculation — first of the prostate secretion, then of the sperm- 

 containing testicular secretion, and, lastly, the seminal vesicle secretion. 



The mucous, slightly alkaline secretion of Cowper's glands serves 

 mainly to lubricate the mucous membrane of the urethra, facilitating 

 ejaculation. To a slight extent it may neutralize the acidity of the 

 urethral mucous membrane. 



The alkaline proteid secretion of the prostate serves to protect the 

 spermatozoa from acidity in the urethra and in the vagina. It is not 

 essential to successful insemination, but it promotes, as Fiirbringer and 

 AValker have shown, the mobility and vitality of the spermatozoa. 



The seminal fluid with actively mobile spermatozoa comes from the 

 epididymis and vas deferens, and perhaps from the mediastinum testis, 

 but not from the testis as such. The spermatozoa do not attain full 

 mobility till 24-48 hours after they leave the testis. They probably re- 

 tain their maximum mobility for four or five days, but this is uncertain. 



The seminal vesicles are not receptacula seminis, though they some- 

 times contain ripe spermatozoa. Their importance is glandular. They 

 produce an alkaline gelatinous secretion, which mechanically helps to 

 force out the spermatozoa, and in some cases helps to retain the sperma- 

 tozoa in the vagina. They should be called, as Kolliker suggested, 

 glandulas vesiculares. 



b. Histolog-y. 



Minute Structure of Femoral Bones. $— J. S. Foot has made a 

 comparative histological study of the femur in the frog, the alligator, 

 the snapping turtle, numerous birds, and numerous mammals. He 



* Quart. Journ. Micr. Sci., lvii. (1911) pp. 1-44 (4 pis. and 1 fig.). 



t Arch. Mikr. Anat., lxxviii. (1911) Festschrift Waldeyer, 2te Abt., pp. 12S-50, 



X Trans. Amer. Micr. Soc, xxx. (1911) pp. 87-140 (9 pis.). 



