EXI'LANATION OF FIGURES. 



CaiiuMa (Irawiiius at the level of the table with Zeiss homogeneous immer- 

 sion (tl)jec-tive 1/12, ocular 12. 



I'art of the material was stained in Hermann's fiuid, the remainder in Flem- 

 ming's fluid. It was stained either with iron hiematoxylin or with safraniu 

 and malachite green. 



Plate I. 

 Talorchestia longicornis. 



T, 1. Restiug spermatogonia. 



T, 2 and T, 3. Spermatogonia! prophases. 



T, 4. Metaphase. 



T, 5-9. Synapsis. 



Idotea irrorata. 



. I, 1. Resting spermatogonium. 

 I, 2 and I, 3. Spermatogonial prophases. 

 I, 4. Metaphase. 



I, 5. Early synapsis. I'arallel strands appear in the networli. 

 I, G. Later synapsis. 

 I, 7-9. Divergence of conjugated chromosomes. 



Oniscus asellns Linn. 



O, 1. Spermatogonial prophase. 

 O, 2. Anaphase. 



Hippa talpoides. 



Hi, 1. Resting spermatogonium. 



Hi. 2-4. Prophases. 



Hi, 5. Metaphase. 



Hi, 6 and Hi, 7. Nuclei of the last generation of spermatogonia. Approach 



of chromosomes in pairs. 

 Hi, 8-12. Post-syuapsis. Gradual divergence of conjugated chromosomes. 

 Hi, 13. Final conversion of chromosomes into the network of the resting 



spermatocyte. 

 Hi, 14. Resting spermatocyte. Nucleoli reduced in size. 



Astacus fluviatilis. 



A, 1. Early spermatogonial prophase. 



A, 2. Late prophase. 



A, 3. Synapsis. Mitochondria in the cytoplasm. 



Homarus vulgaris. 



Ho, 1. Resting spermatogonium. 



Ho, 2. Early spermatogonial prophase. 



Ho, 3. Very late prophase. 



Ho, 4. Spermatogonium of the last generation. Approach of the chromo- 

 somes in pairs. 



Ho, 5. Synapsis. Longitudinal conjugation of chromosomes. Mitochon- 

 dria in the cytoplasm. 



Ho. G. Diverjrence of the pairs. 



Ho, 7. Resting spermatocyte. Mitochondria in the cytoplasm. 



