LEPTODORA HYALINA. 49 



ON THE HABITS AND LIFE-HISTORY OF 

 LEPTODORA HYALINA. 



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

 PROFESSOR OF ZOOLOGY IN THE OWENS COLLEGE. 



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 Weismann, " On the Structure and Life-history 

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

 wissenschaftliche 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. 



Weismann first met with Leptodora in Lake Constance during the 

 summer of 1873, and supposing it to be new to science devoted much 

 time and trouble to working out its life-history during this and the 

 following year. The principal results to which he was led, as contained 

 in the paper above referred to, are as follows. 



For the capture of Leptodora Weismann employed a fine net 

 dragged immediately beneath the surface of the water; he notes that 



References to Plate III. 



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

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



e. Labrum, or upper lip. 

 /. Carapace. 



g. Compound eye of adult. 

 h. Larval or Nauplius eye. 

 i. Intestine. 

 fc. 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, antennae, b, and mandibles, 

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

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

 distinguish the Nauplius larva of Leptodora from the Nauplii of other 

 Crustacea. 

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

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

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

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

 the rudiment of the c impound 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 mandibles, c, has under- 

 gone not only a relative but an actual decrease in size ; the compound 

 eye, g, has gre itly increased in size ; the abdomen is segmented ; 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 sprin" brood from all other generations, and as mv sole object 

 in giving 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'a 

 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. 



H 



Anterior pair of antennae, or 

 antennules. 



b. Posterior pair of antennae, 



or antennae proper. 



c. Mandibles. 



d. Thoracic appendages. 



