ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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other points of difference, tliat of the female is smaller and weaker than 
that of the male. In the former, indeed, it has only to prick the plants 
to draw out the liquids necessary for food ; in the latter it has to help a 
delicate worm to make an active passage through the tissues of the plant 
when a parasitic is about to be exchanged for a free mode of life. 
Similar differences, due to similar causes, are to be seen in the stylets of 
the first and second larvee ; the first is very agile and lives for a time 
freely in the earth ; the second is sedentary or parasitic, and has a 
smaller flexible stylet. The changes are effected in the organ when the 
worm sheds its chitinous cuticle. 
y. Platyhelminth.es. 
Organization of Accelous Turbellaria.* — Prof. L. Graff has a 
preliminary notice of the results of his work on this group of worms. 
He has been led to form a new classification, in which the first family, 
that of the Proporida, consists of Accela with one genital orifice ; Proporus 
has no bursa seminalis, Monoporus (g. n.) has one ; the type of the last 
is P. rubropunctatus. The second family — the Aphanostomida — contains 
three genera, all of which have two genital orifices and a bursa semi- 
nalis ; Aphanostoma has no chitinous piece to the bursa, Convolula has 
one, and Amphichserus (g. n.) has two ; the type of the last genus is 
C. cinerea. 
If the epidermis be fixed by chrom-aceto-osmic acid and stained 
with haematoxylin, it is possible to perfectly preserve unicellular glands, 
the nature of which has been generally misunderstood. It is certain 
that all Accela have the three layers of muscular fibrils described by 
Delage in Convoluta roscoffensis. All forms studied in the fresh state 
were seen to have a ventral mouth and a simple pharynx ; hitherto its 
presence has been denied in some members of the group. Three types 
of structure may be distinguished in the parenchyma; in some it is 
reticulated, and there is a large number of free cells ; in others the 
central parenchyma is a syncytium very rich in nuclei, but without any 
free cells, while the peripheral portion is a tissue of rounded cells 
closely packed against one another. In the third type the body is 
filled with a nucleated syncytium, in which amoeboid cells swim. 
From the morphological point of view the free cells are considered 
as mesodermal elements still inclosed in the endoderm ; they have a 
digestive function. In more advanced forms ( C . paradoxa) they lose 
this function, and become peripheral elements of support, while the 
reticulum alone performs the digestive functions. 
Prof. Graff made use of Delage’ s gold method and found that it gave 
the best possible results ; the want of certainty, however, is a serious 
objection. On the whole, the author agrees with the results of Delage, 
but he cannot find the cerebral cavity described by the latter. Pro- 
porus or Monoporus show some remarkable differences in the structure 
of the central nervous system. 
The frontal organ of Delage is not an organ of sense, but part of a 
gland ; the “ nerve-cells ” and “ fibres ” are merely formed by parenchy- 
matous tissue distributed among the excretory ducts of this gland. It 
* Arch. Zool. Exper. et Gen. ix. (1891) pp. 1-12. 
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