CYTOLOGY OF ANISOLABIS MARITIMA BON. 237 



Embryos were removed from their chorionic coverings before 

 fixation in Flemming's fluid. 



The abundance of material, the large number of preparations 

 made, and the variety of methods employed lead the author to 

 believe that his results are fairly accurate. 



All drawings were made with the aid of a camera lucida, using 

 a 1.5 mm. Zeiss apochromatic objective and a 20 X compen- 

 sating ocular. This gave an initial magnification of 3300 

 diameters. The drawings were reduced in the reproductions, 

 plate XXIV about one-third and plates XXV and XXVI about 

 two-fifths. 



4. THE GONADS 



Each testis consists of two long narrow tubules surrounded 

 by a fat sheath. The length and narrowness of the tubules 

 gives a good seriation of stages from the blind tip to the bottom 

 where the sperm pass into the vas efferens. Near the blind or 

 cephalic end of the tubule is a large apical cell, surrounded by 

 young cysts of spermatogonia. These younger spermatogonial 

 generations are larger cells and better for spermatogonial counts 

 than those in cysts more caudad. The cysts are clearly marked 

 off from one another by distinct walls. The spermatocytes 

 undergo considerable growth in size and their cytoplasm acquires 

 a large amount of mitochondria. The spermatocyte cysts occupy 

 by far the greater part of the tubules in nymphal males. At 

 no time during the growth period do the chromosomes disappear 

 or lose their staining powers. The transition from ultimate 

 spermatogonia to the formation of the spermatids must be rather 

 slow, inasmuch as every stage in the conjugation of the chromo- 

 somes and the formation of the tetrads may be found in the 

 testes of a 'single nymph, previous to the final moult. This is 

 in marked contrast to many insects, in which the syndetic stages 

 are very rare and difficult to find. One fortunate condition in 

 the study of Anisolabis is the fact that each testicular tubule 

 contains a large number of cysts and that each cyst shows slight 

 variations in its meiotic phase. 



