1604 
tables in “Directions for the use of the astrolabe”’, some simplification 
being introduced to enable it to be used for every year, leap-year 
or ordinary year alike. 
It is most probable that the copies of the “Directions” and of 
Zacvuto’s tables which have been found were preceded by older 
editions. In a letter written on May 1st 1500 by Prpro Avarnz CABRAT’s 
mate, reference is made to a determination of latitude in Brazil at 
south latitude 17°, which, as he writes, is made according to the 
rules of the astrolabe, and of which the results correspond entirely 
to the data in the tables of the Munich copy of the “Directions”. 
It cannot be ascertained with certainty from what source ZAcuro 
borrowed the tables referred to above, but BENsAUDE quotes a number 
of manuscripts, revealed by the researches of STEINSCHNEIDER, which 
were written after the preparation of the Alpbonzine tables in 1252, 
upon astronomical subjects and instruments in Spain, Provence and 
Portugal, principally by Arabs and learned Jews of the 14" and 15% 
centuries. Zacuro follows upon these writers, so that le was pro- 
bably enabled to compile his tables from the data which they supplied. 
It may therefore be concluded with the greatest probability, that 
the Portuguese owed their knowledge of the science of navigation 
at the time of their great discoveries, not to German scholars, but 
to the high scientific attainments of their own compatriots. 
Zoology. — “Critical and theoretical considerations about the origin 
of the primary foetal membranes in Vertebrates.’ By Dr. 
Dan. pr LANGE. (Communicated by Prof. J. F. van BEMMELEN). 
(Communicated in the meeting of March 25, 1916). 
The presence of primary foetal membranes in Sauropsida and 
Mammalia has been considered for a long time as a characteristic 
of great systematic value and has led to the division of Vertebrates 
in Amniota s. Allantoidea provided with primary foetal membranes 
and Anannia s. Anallantoidea without these membranes. Members 
of the last group (Cyclostomata, Pisces and Amphibia) are also 
named Jchthyopsida, since they live wholly or partly (as larves) in 
an aquatic environment where they breathe by gills, gill-breathing 
never being present in the first group. Of course there exist Ammniota 
which have become adapted to an aquatic life (turtles, marine 
Saurians and especially Cetaceans), but as in them lungbreathing 
has always been preserved and never ‘been substituted by gill- 
