ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
385 
possess a double mechanism of secretion, i.e. a muscular and an osmotic ; 
(5) whether secretory nerves exist or whether secretion is ever a function 
of the gland-cell, must be considered at present an open question. 
Present Status of Anatomy.* — Under this title Prof. J. Playfair 
McMurrich publishes an interesting historical account of the progress 
of the science from the time of Yesalius to the present day. His con- 
clusions may be gathered from the following sentences : — “In the past, 
anatomy was human anatomy ; to-day, it is synonymous with morpho- 
logy.” “ Descriptive anatomy is not necessarily a science ; it con- 
stitutes merely an aggregate of facts upon which deduction may act ; 
and it is the sum-total of the observations and deductions that con- 
stitutes the science.” 
Tunicata. 
Appendiculariidae of the Straits of Messina.j — Dr. H. Lohmann 
has made extensive series of observations on the minute forms of the 
surface waters in the Straits of Messina, with a special view to deter- 
mining the causation of the seasonal variations in number, and the 
character of the forms found at different seasons. In the neighbourhood 
of Messina 26 species of Appendiculariidae were found, mostly those 
characteristic of equatorial waters, but including also typical forms of 
Fritillaria borealis. The mixed character of the fauna was further 
emphasised by northern forms of Geratium. By the use of closing nets 
at various depths, it was proved that the periodic partial disappearance 
of the Appendiculariidae, already familiar to Mediterranean naturalists, 
is confined to the superficial layers of water, all the characteristic forms 
being present in the lower layers. The cause the author believes fc> 
be not variations in temperature acting directly, but variations in the 
amount of Plankton Algae. Observation showed that the period of 
great faunistic wealth is preceded by the growing period of the Algae. 
The Algae reproduce rapidly, and the active forms rise to the surface 
in search of them, and being well fed reproduce rapidly. As the Algae 
diminish in number, the Appendiculariidae and the other forms 
diminish also in number, and sink to the lower layers of water. A 
depth of 100 metres seems to be the limit to which the Appendiculariidae 
sink. 
Four species of Challenger ia, which has not hitherto been described 
for the Mediterranean, were discovered during the observations. 
Epicardium in Ciona intestinalis4 — D. Damas has investigated 
the character, relations, and development of the space which surrounds 
the viscera in this tunicate. He finds that it is double and not single 
as previously described. The two spaces do not communicate with each 
other, but open into the branchial sac by two orifices. They are of 
very unequal size, the left being much larger than the right. The author 
believes that these two spaces together correspond to the epicardium as 
described by Yan Beneden and Julin in Clavelina. Willey’s statement 
that the epicardium is wholly absent in Ciona is explained by the fact 
that the organ, as above defined, develops at a late period and was not 
* Amer. Nat., xxxiii. (1899) pp. 185-98. 
t SB. Akad. Wiss. Berlin, 1899, pp. 384-400. 
j Arch. Biol., xvi. (1899) pp. 1-25 (3 pis.). 
