ZOOLOGY AND BOTANY, MICKOSOOPY, ETC. 
25 
more, iu young animals every muscular rudiment consists of a strand of 
mesenchyme cells, and the author notes that though the muscle round 
the inhalant aperture has a purely mesenchymatous origin, it exhibits 
histological characters which the Hertwigs describe as belonging to 
epithelial or mesoblastic musculature. Finally, heart and pericardium 
also arise from the mesenchyme. In his account of the history of the 
genital strand, Seeliger emphasizes the fact that the hermaphrodite 
apparatus of the organism and the mesoderm of the buds arise from 
the same rudiment. The memoir concludes with some notes on the 
formation of the Pyrosoma colony. 
Heterotrema Sarasinorum.* — Dr. K. Fiedler gives an account of a 
new genus of Synascidians, which was discovered by the Doctors Sarasin 
during their visit to Ceylon. It belongs to the family Distomidm, as 
defined by Herdman, and stands nearest to Bistoma itself, but it differs 
from it in having the efferent orifice merely surrounded by a smooth 
layer of circular muscles, the teeth being absent ; it has also a trifid 
anal languette, which is wanting in Bistoma. The author gives a 
technical account of the new genus and species, as well as numerous 
details regarding its anatomy. 
Arthropoda. 
Peculiar Swimming Movements of Blood-corpuscles of Arthro- 
pods.! — S' Dewitz has noticed in certain Arthropods phenomena 
which led him to believe that the blood-corpuscles are able to swim 
freely in the blood-fluid. In the hinder wings of a still uncoloured 
Tenehrio molitor, which has just passed the pux3al stage, the matrix-tissue 
of the wings begins to disappear. Processes radiate out from the proto- 
plasm of the cell-body around the nuclei, and pass into the adjoining 
matrix-cells. This meshwork is filled with blood. The corj^uscles are 
generally narrowed at either end, and sail with one tip directed forward 
through the meshwork. The author enters into a good deal of detail 
as to his observations. As to the cause of the movements there is con- 
siderable diffieulty. No cilia could be detected, nor any regular undu- 
lations of the surface, such as Brock has observed in the s] 3 ermatozoa 
of a Mollusc ; it is possible that they take up and again drive out 
blood-fluid, and in this way effect their movements. It is clear that the 
blood-corpuscles of Arthropods have a greater power of movement than 
those of Vertebrates, for they do not move in a closed vascular system, 
and can only regain their paths by depending on their own activity. 
It is not quite certain whether the active movement seen by Max 
Schultze in the red blood-corpuscles of quite young chicks was a 
swimming or an amoeboid-creeping movement. 
Vision of Arthropods.^ — Dr. D. Sharp, after giving an account of 
Prof. Plateau’s valuable experiments on the vision of Arthropods, sum- 
marizes his impressions. Insects in motion are guided largely by the 
direction of light, and the existence of light and shade. When walking 
they are guided by a combination of light-impressions and tactile- 
* Zool. Jahrb., iv. (1889) pp. 857-78 (1 pi.). 
t Zool. Anzeig., xii. (1889) pp. 457-04. 
X Trans. Eutoiiiol. SSoc. Lond., 1889, pp. 393-408 (1 pi.). 
