No. 3.] STUDIES ON CEPHALOPODS. 249 



ter to get hundreds of ripe ova from the egg-reservoir. The eggs, 

 when ripe, shine through the thin wall of the body underneath the 

 mantle, and easily roll out through an incision in the wall, as the 

 shot would do through a similar opening in the sac which con- 

 tained them. A search for the spermatophores may then be made 

 in the adult male, which, in the reproductive season, carries sev- 

 eral bunches in the inside of the mantle chamber. If the search 

 in the mantle chamber fail, we can usually get quantities of them 

 in the reservoir, through the thin walls of which can be seen, regu- 

 larly arranged, white, elongated, spindle-shaped spermatophores. 

 Search for a male is often rendered unnecessary, for a number of 

 spermatophores are usually carried by the females on the inside 

 of the arms, and may usually be found on the little horseshoe- 

 shaped prominence on the inner surface of the outer buccal mem- 

 brane of the same animal from which the eggs were taken. This 

 is a matter of great convenience to the investigator, for a single 

 female with well-matured eggs will usually have spermatozoa 

 enough to fertilize all the eggs. Taking hold of the bunch of 

 spermatophores with the forceps and shaking them into a dish 

 with a little water in it, the spermatozoa can be liberated easily. 

 The process can be facilitated by cutting the spermatophores 

 with scissors into a few fragments. By pouring the water, frag- 

 ments of the spermatophores and all, over the eggs, and mixing 

 them thoroughly, the artificial part of the fertilization may be 

 said to have been accomplished. If one take an egg and a few 

 drops of the water after this process and examine them under 

 the microscope, one will see a multitude of spermatozoa covering 

 the surface of the ovum, and with little perseverance one can 

 follow the penetration of the sperm-cell into the ovum through 

 the micropyle. Between one and two hours after the mixture 

 of the sperm and the ova, the first furrow of the cleavage was 

 observed, and thence at intervals of five to ten minutes, the 

 succeeding furrows of cleavage were introduced, the interval 

 between the two successive furrows becoming shorter and 

 shorter as the stage advances. 



After the majority of ova have commenced to divide, it is 

 necessary to change the water frequently, particularly when a 

 large number of eggs are kept in the same vessel. 



In order to separate the blastoderm, the egg at any given 

 stage of division was killed by a mixture of sea-water, acetic 



