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POPULAR SCIENCE REVIEW. 
How can Dr. Dawson imagine for a moment that he is rendering the student’s 
path more easy hy talking of cell-structures, organisation, and vital force ? 
When the Doctor tells his readers that animals differ from plants in being 
reproduced by ova, and not by seeds, he lays himself open to the charge of 
ignorance of the commonest principles of physiology. We trust that when 
this gentleman again appears in the capacity of a teacher of philosophical 
zoology, he will have enlightened his mind by a careful study of the re- 
searches of those who, without excessive ambition, have been conscientious 
enough to ascertain the truth of statements before they have committed 
themselves to generalization. 
Peculiar Struchires in the Seminal Fluid of lanthina. — Herr Fritz jMiiUer, 
in a paper which appeared in Wiegmann^s Archer, and has been translated 
by Mr. Dallas, describes some very peculiar structures which have been 
observed by him in the seminal fluid of lanthina. In this secretion numer- 
ous vermiform bodies may be seen (even with the naked eye) swimming 
briskly about. Their length is about half a millimetre. With the aid of the 
lens, two sharply indicated divisions may be observed, which foim a sort of 
head and tail. The head occupies one-fourth of the total length ; it is some- 
times of a pretty regular conical form ; sometimes furnished at its posterior 
thicker portion with irregular processes ; and sometimes projects anteriorly in 
a double, instead of a single point. It contains numerous granules of various 
sizes, with dark outlines, which render it rather opaque, and no distinct 
membrane could be perceived surrounding it. The tail, about three times as 
long as the head, is anteriorly much narrower than the hinder margin of the 
head, but becomes gradually enlarged posteriorly, and termmates in a rounded 
end ; it is almost completely opaque, and is densely clothed with delicate 
hairs of about of a millimetre in length. These hairs are seen to move 
rapidly, but do not strike in the same direction, as in the case of 
the cilia ; on the contrary, they wave and mingle together irregularly, so 
that they cannot be regarded as the cause of the rapid movements by which 
the structures pass through the water in large curves. At a distance of 
nearly twice the length of the head from its apex, it is preceded by a conical 
point with delicate but clearly marked outlines, from which a perfectly trans- 
parent membrane waves down to about the middle of the head, like a flutter- 
ing veil. Sometimes an extremely delicate longitudinal striation is observed 
in this membrane. Posteriorly its outlines are so evanescent that it can 
seldom be traced to its hinder margin. In the vicinity of the conical point, 
several little lobes, resembling narrow cilia, separate from the membrane. 
While the structure is swimming these little lobes oscillate rapidly and 
powerfully, and the whole membrane is in lively oscillating movement. Herr 
Muller first regarded these bodies as parasites, until having invariably found 
them in the semen, he was led to regard them as an essential constituent 
of this secretion. Besides, on several occasions, he succeeded in breaking up 
several tails into groups of unmistakable seminal filaments. He concludes, 
therefore, that they are “ part and parcel ” of the semen, and asks, are they 
the formative organs of the seminal filaments, from which these, subsequently, 
when mature, separate ? or are they spermatophora around which the mature 
seminal filaments have collected. 
Crustacea of the Glacial Epoch in the Scandinavian Lakes. — M. Sars has 
