INTRODUCTION 



Subscribers are now receiving the sixth full issue of the General Embryologi- 

 cal Information Service, in which all the data over the year 1955 are pubhshed. 

 We have tried to make this issue as complete as possible by extending our hst 

 of collaborators. New relations were opened with India, Australia and New 

 Zealand, and with several institutes in Japan. Contact was made with several 

 Universities in Latin America, while contact was re-established with Russia and 

 Czecho-Slovakia. We also tried to extend our relations with medical and vete- 

 rinary institutions where embryological work is done by some staff members 

 only. This action has led to an increase in the number of collaborators from 

 946 (1953) to 1095 (1955), and to an increase of the number of collaborating 

 institutes from 349 (1953) to 439 (1955). 



The biennial collecting of data for the G.E.I. S. makes it more difficult to 

 keep our list of addresses uptodate. We therefore request all collaborators 

 to keep us informed about any change in address or position. 



The preparation of the extensive manuscript of the Normal Table of Xeno- 

 pus laevis (see further under General questions and announcements on page 

 184) has heavily overloaded our staff this summer, resulting in a delay in the 

 preparation of the manuscript of the G.E.I. S. We offer all subscribers our apo- 

 logies for this delay in the appearance of this issue. 



As mentioned in the 1953 issue, the subscription for the 1955 issue of the 

 G.E.I.S. will include the full issue 1955 and the supplement 1956. In the sup- 

 plement 1956 new data for the "Supply and Demand Service for Laboratory 

 Animals" will be published, so that those interested are requested to send in 

 all available data before August 1st, 1956. 



We should like to acknowledge our sincere thanks to those collaborators who 

 have helped us to open new relations with embryologists not previously 

 included. 



P. D. NIEUWKOOP 



