LEPTODORA HYALINA. 15 



ON THE HABITS AND LIFE -HISTORY OF 

 LEPTODORA HYALINA. 



BY A. MILNES MARSHALL, D.SC, ETC., 

 PROFESSOR OF ZOOLOGY IN THE OWENS COLLEGE. 



Read before the Society March 2, 1880. 



In view of the approach of another season for obtaining specimens 

 of this new and specially interesting Entomostracon, and for investigating 

 its life-history, the following notes of the Continental experience and 

 study of this creature may be found of service. They are extracted from 

 the German memoir by Weismaun, " On the Structure and Life-history 

 of Leptodora Hyalina," which appeared first in the Zeitschrift fiir 

 wissenschafthche Zoologie for 1874, and was subsequently republished in 

 a separate form. This memoir, a carefully written and detailed treatise 

 of 70 pages, illustrated by six large plates, is by far the most complete 

 and accurate account of Leptodora that has yet appeared. 



References to Plate III. 



The Figures, which are copied from Bronn's Klassen und Ordnungen des Thier- 

 reichs, represent three stages in the development of the spring brood of Leptodora. 



a. Anterior pair of antennaB, or 



antennules. 

 6. Posterior pair of antennae, 



or antennjB proper. 



c. Mandibles. 



d. Thoracic appendages. 



e. Labram, or upper lip. 



/. Carapace. 



Q. Compound eye of adult. 



h. Larval or NaupUus eye. 



i. Intestine. 



fe. Ovary. 



Fig. 1.— First stage in the development of the spring brood, seen from the 

 dorsal surface. This earliest or Nauplius stage possesses only three 

 pairs of jointed appendages— antennules a.antennse ii.and mandibles 

 c. The great size of the second pair, the antennae, h, is obviously 

 correlated with their large size in the adult, and is a point serving to 

 distinguish the Nauplius larva of Leptodora from the ^auplii of other 

 Crustacea. 



Fig. 2. — A somewhat older larva seen from the right side. In addition to the 

 marked increase in size, the most important changes are the greater 

 development of the thoracic appendages, a. the appearance of the 

 ovary, fc, (all the spring brood are said to develope into females,) and 

 the rudiment of the compound adult eye, g. 



Fig. 3,— A still older larva, seen from the right side. The thoracic appendages, d, 

 have now grown very considerably; the carapace, /, has begun to 

 appear ; the limb-like portion or palp of the mandib es, c, has under- 

 gone not only a relative but an actual decrtase msize; the compound 

 eye, g. has grently increased in size ; the abdomen is segmenien ; and 

 the alimentary canal has acquired the arrangement characteristic of 

 the adult. 



In Figs. 2 and 3 the appendages of one side only of the body are shown. 



Note.— In the original figures, which are very roughly drawn, the larval or 

 Nauplius eye is not distinctly shown. As its presence is of extreme importance as 

 distinguishing the spring brood from all other generations, and as my sole object 

 in givmg these figures is to facilitate the recognition of the larva, I have inserted 

 this eye in the figures in the position which it holds according to Weismann's 

 descriptions. I hope that before long some of the Birmingham Naturalists may be 

 able to give us more satisfactory figures of these developmental stages. 



A. M. M. 



