KOFOID : DEVELOPMENT OF LLMAX. 



II. METHODS. 



The most successful method of keeping the animals in captivity was 

 found to be as follows. A tin box with proper ventilation is filled to 

 the depth of one inch with clean sand, which forms a suitable substratum 

 for the retention of moisture. On this is laid down a sheet of moss, to 

 whose under surface the earth still adheres. The leaves of the common 

 plantain furnish acceptable food, and, when this is no longer available, 

 fresh cabbage leaves and apple parings can be used. The eggs, which 

 seem more often to be laid at night, are found iu clusters in the soil, or 

 cunningly packed away in the moss itself. The rate of development is 

 such at the ordinary temperature of the laboratory that the eggs col- 

 lected in the morning will generally be found to have already reached 

 the early stages of cleavage, while gastrulation progresses during the 

 second day, and is completed early in the third. During the first week 

 of captivity the slugs furnish eggs in great abundance ; but after that 

 time the number diminishes and the quality deteriorates so rapidly that 

 it is imperative that a new colony be secured. Abnormalities in the 

 living egg show themselves in the early stages by a loose assemblage of 

 the cells, and the increasing opacity of the embryo. 



Before hardening the embryo, it is necessary to free it from the en- 

 velopes and albumen which surround it. As the eggs of Agriolimax 

 agrestis are much smaller than those of Limax maximus, it was not 

 possible to employ the method described by Miss Henchman ('91) for 

 shelling the eggs. But by inserting two fine cambric needles in one 

 holdei", so that the distance between the points is less than the diameter 

 of the unshelled egg, it is possible to hold the egg between these two 

 needles and pierce it by a third. A quick shear-like cut with the third 

 needle against one of the other two tears open one side of the egg and 

 allows the albumen and the ovum to escape from the envelopes. It is 

 very desirable not to entangle the embryo in the viscous matter between 

 the inner and outer envelope, for it is almost impossible to remove this 

 when it is once attached to the embryo. The albumen interferes with 

 section-cutting and obscures whole pi'eparations, so that it is necessary 

 to remove it entirely. This for a long time presented a most serious 

 obstacle to my work. "Washing off the albumen with water is a very 

 slow and tedious process, and not always successful. Some of the eggs, 

 after treatment with Merkel's or Flemming's fluid for a short time, were 

 washed with hypochlorite of soda to rid them of the albumen. The 



