No. 12. — Maturation, Fecundation, and Segmentation of Limax 

 camjpestris, Binney. By E. L. Mark.* 



The observations of the past five years t on the earliest stages in 

 ontogeny have contributed more to the solid advancement of biological 

 knowledge, than those of any corresponding interval since the studies 

 of Max Schultze and others paved the way to a science of Biology. 



More refined methods of research have resulted in more exact knowl- 

 edge of phenomena. A closer study of details has opened the way to 

 a broader comprehension of their significance. 



It was with the hope of adding something to the empirical acquisi- 

 tions in this field, that I undertook the studies whose results follow. 



A. OBSERVATIONS. 



The eggs of Limax campestris, Binney, are found in moist places, pro- 

 tected from the drying influences of direct sunlight and currents of air. 

 They are frequently met with in the vicinity of a small stream, some 

 stagnant pool, or in low meadow-land. Open woodland presents favor- 

 able conditions for their development, affording sufficient warmth, and 

 preventing too direct sunlight and constant winds. In such locations 

 loose piles of decaying wood are often chosen for the deposit of eggs. 

 At other times, when the ground is less protected, they may be found 

 under loose stones, or even in the bed of some spring-time water chan- 

 nel, where crevices in clumps of earth afford protection. The most of 

 the material which I have studied was obtained from slugs kept in 

 confinement. These were collected from partially shaded ground with 

 scanty grass-growth, in the vicinity of Fredonia, N. Y. A portion, 

 however, were from low grass-land near the Museum of Comparative 

 Zoology in Cambridge. 



* I desire to acknowledge my indebtedness for the use of books to the extensive 

 libraries connected with the University, as well as to the Boston Society of Natural 

 History, the Boston Public Library, and the Boston Medical Library. I am under 

 obligations to the librarians of all these institutions for personal or official favors, for 

 which I take this opportunity of expressing my thanks. 



t The unfortunate delays which have attended the publication of this paper are 

 liable to mislead the reader, unless it is borne in mind that it was prepared early 

 in 1879. See a preliminary notice in Zool. Anzeiger, 2 Jahrg., p. 493. 



VOL. VI. — NO. 12. 



