It is generally assumed that the forces which bring about gastrulation arise from the pressure of dividing cells acting in a plane which passes through the apical and basal poles of the embryo. Morgan ( '27) has expressed it: "AS the cells of one hemisphere or part of it, are turned in, the pressure between the cells of the other hemisphere will be lowered, since the line o f celZs,l so to speak, becomes longer and the smaller cells will be expected to expand, and this in fact occurs." This idea is implicit in the thinking of Rhumbler ( '02), Biitschli ('15), and Assheton ( '16). On the contrary, actually the larva is three-dimensional, and it strikes one that there is something a little false in a simplification which considers forces acting in a plane which has no natural demarcation. I n order to test whether the conventional assumption might have an element of truth in it, a series of experiments were carried out with the larvae of Dendraster excentricus, in which parts of the embryo above the vegetal plate were cut away. If the invagination were due to pressure exerted in a median animal-vegetal plane, then it would depend upon the integrity of the hollow sphere or at least upon that of the 'line of cells,' so that if part of the early gastrula were removed, the beginning inpocketing could not persist but would tend to collapse. The first four figures shown in the plate 'Italics are ours.

No abstract

A work has been done on the effects of steroid hormones on the endocrine glands and on the relation of endocrine changes to carcinoma of the breast in laboratory animals, few comparable data are available for man. Information about the human anterior pituitary is particularly scarce, despite the fact that this organ is assigned a key role in many theories of hormonal interaction. Therefore the autopsy material of the Massachusetts General Hospital for the past ten years has been reviewed, and the hypophyses from all patients having a history of carcinoma of the breast collected. Twentyseven hypophyses were found, from women who either received no steroid hormone therapy, received estrogens alone, were castrated, or were treated by a combination of estrogens and castration. Since four of these glands contained metastatic carcinoma, which precluded quantitative cell counts, the present report is a study of the remaining twenty-three pituitaries.Some hypophyses had already been fixed in Zenker's or Helly's fluid, embedded in paraffin, and serially sectioned. For these glands no gross weights are available. Other glands that had been preserved whole in 10 per cent formalin were weighed on a torsion balance after removal of the pituitary stalk and dural membranes. They were then divided in the midsagittal plane; the left half was further divided into three sagittal blocks of equal thickness while the right half was cut into two blocks in the median plane. Tissues were chromated prior to paraffin embedding and sectioning. In those pituitaries that had teen preserved whole, a differential count was performed on one sec-