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J. 0. Wakelin Barratt and G. Arnold 
Fig. 1. Normal cell of Sertoli. The cell is in contact with tlie basement mem- 
brane of a seminiferous tubule. The nucleus is large, contains a well-defined nuclear 
membrane within which is a large nucleolus. The chromatin of the nucleus is distributed 
in fine granules, three of four larger masses being present in addition; the forrner are 
faintly stained, the latter stain deeply. The cytoplasm is moderately abundant; it is 
finely reticular in aspect, and its outlines are not clearlv defined below. 
Fig. 2. Normal spermatogonium in non-dividing stage, situated on the base- 
ment membrane of a seminiferous tubule. The nucleus presents a well-defined nuclear 
membrane, within which chromatin is arranged in the form of numerous irregulär 
masses, some of which being out of focus are represented as shadows. A nucleolus is 
seen but no definite linin network. No intranuclear body is present. The cytoplasm 
of the cell is fairly abundant and finely reticular. No archoplasmic vesicle is seen. 
Fig. 3. Normal dividing spermatogonium. The cell which lies on the basement 
membrane of a seminiferous tubule is of larger size than the preceding cell. The nuclear 
membrane lias disappeared. The cliromosomes which are very numerous (about thirty 
in number), and are arranged on the equatorial plane of a spindle have the shape of 
short thick v-shaped rods, some of which show signs of fission. Around the chromo- 
somes is a clear area. The cytoplasm is finely reticular and its outlines are sharply 
defined. 
Fig. 4. Normal young spermatocyte of the first Order situated at a distance 
of 12 u from the basement membrane of a seminiferous tubule. The nuclear membrane 
is indistinct. The nucleus contains a linin network upon the threads of which are 
arranged masses of chromatin of varying size, five of which are conspicuously larger 
than the rest. No intranuclear body or nucleolus can be recognized. The cytoplasm 
is abundant, and exliibits a fine reticulum, the meshes of which are somewliat coarse. 
Fig. 5. Normal spermatocyte of the first Order situated at a distance of about 
12 fi from the basement membrane of a seminiferous tubule. The cell, which is larger 
than the preceding. is in the spireme stage. The nuclear membrane is somewhat indi- 
stinct. The nucleus contains a linin network around the threads of which are arranged 
masses of chromatin, which are larger and more numerous than in the preceding figure ; 
an intranuclear body is also seen and a nucleolus. The cytoplasm is abundant, ex- 
liibits as before a fine reticulum, and contains an archoplasmic mass, staining with 
acid dyes, as well as two small darkly stained granules, the significance of which is 
uncertain. 
Fig. 6. Normal dividing spermatocyte of the first order, in late spireme stage, 
situated about 30 fi from the basement membrane of a seminiferous tubule. The cell 
is still larger than tliat shown in the preceding Figure. The nucleus exhibits a nuclear 
membrane, within which chromatin is arranged upon looped linin threads ; an intra- 
nuclear body and nucleolus are also seen. The cytoplasm, which is finely reticular, is 
clearer than in the preceding Figure and contains an arclioplasm near which is a darkly 
stained granule. 
Fig. 7. Normal spermatocyte of the first order, undergoing heterotypical mitosis, 
situated towards the basement membrane, about three-fifths of the distance from tliis 
to the lumen of a seminiferous tubule. The nuclear membrane lias disappeared. The 
chromosomes of which about thirteen can be seen, of varying shapes are arranged 
in a characteristic manner on the equator of a well-defined spindle, which presents 
a centrosome at each pole. The cytoplasm is somewhat granulär in aspect and presents 
a loose meshed arrangement. 
