153 



The central collection will be at the disposal of all embryologists, a s 

 they can study the material at the Hubrecht Labora- 

 tory, and parts of the collection may be borrowed 

 under special conditions (vid. section B). 



Besides a very detailed card-index we are composing a more general 

 catalogue of the whole collection, which will in due course be sent to all 

 embryological institutes, in order to make the collection more easily accessible. 



We like to draw your attention to the very great advantages 

 of a Central Embryological Collection, with accomodation 

 for embryologists to study it. Such a collection has a much higher value than 

 individual small collections, distributed all over the world. We therefore 

 would like to ask from you all possible help and collaboration in increasing 

 the value of our Collection. 



B. Conditions for borrowing. 



1 . Slides 



a. If they do not consist of very important and rare material, may 

 be borrowed for 1 year at the utmost, time for shipment not 

 included. 



b. The receipt, added to the consignment, must be returned b y 

 return of postage, after having been controlled and signed. 



c. The shdes have to be packed safely on returning. 



d. In case of high forwarding-charges they have to be partly carried 

 by the appUcant. 



2. Material 



may be borrowed and studied under the same conditions, but has 

 to be returned as such or in the form of shdes, which become part 

 of the central collection. 



IV. The Normal Table of Xenopus laevis 



All collaborators are at present in the possession of the material to be 

 elaborated, a hst of external features (composed by Dr P. D. Nieuwkoop and 

 J. Faber). a reprint of the series of illustrations as they will appear in their 

 definitive form (made by J. Faber and J. J. Prijs) and a photostat of the 

 Normal Table of Triton taeniatus by Glaesner, which serves as an example 

 of the way of redaction of the different contributions. We are looking forward 

 to receive the first contributions from our collaborators towards the end 

 of 1951. We ask the collaborators to send us at the same time a list 

 of the literature on Xenopus (and on Amphibia in general) which they 

 have used in the preparation of their subject, or which might be of use to other 

 investigators working in the same field. 



In the list of collaborators the place of Mr W. Steyn (Bloemfontein, South- 

 Africa) has become vacant, so that we are now looking for two new 

 collaborators, who are wilhng to undertake respectively: 



1. the development, till the beginning of metamorphosis, of mouth and 

 pharyngeal cavity (including thyroid gland, thymus, lungs) (formerly assigned 

 to Dr R. M. Rosenbaum — Cambridge, Mass., U.S.A.) and 



2. the development, till the beginning of metamorphosis, of the nephroic 

 and gonadal system (formerly assigned to Mr W. Steyn). 



Investigators who, by any chance, might be concerned with these or 

 related investigations in Anura, would be most welcome to 

 join our international team-work. 



