18 LEPTODORA HYALINA. 



the most important larval stages of Leptodora accompany this 

 paper, in the hope that they may facilitate the recognition of the 

 forms when actually met with. 



The wintei- ova, it appears, give rise in March or April to larvae 

 which hatch in the form of Nauplii ; these moult several times, and 

 gradually acquire the form ct the adult. This xpring brood maybe always 

 recognised by the fact that they retain even when adult the median eye 

 of the Nauplius, in addition to the large double compound eye of the 

 adult ; the larval eye persisting as a small black spot on the under 

 surface of the brain. The spring brood gives rise to females only ; these 

 females produce summer ova which develope into adults, and produce 

 other summer ova, and so on ; males do not appear until the autumn, 

 and even then are much scarcer than the females. 



At the end of his paper Weismauu gives a Ust of all the localities in 

 which Leptodora had been observed up to the date of his paper, 1874. 

 The first specimens were found by Focke in 1844 in the town moat of 

 Bremen, which is described as being clear water more than 100 feet 

 Mride, and moderately deep. Lilljeborg foimd it in Sweden in 1860. 

 The males were first discovered by MiiUer in 1867 in Danish lakes, and 

 in Lakes Geneva and Constance. In 1868 Wagner found it in a Eussian 

 lake near Kasan, and, ignorant of its previous discovery, re-named it 

 Hyalosoma dux. It has also occurred in Lake Maggiore, in Italy, but 

 according to Weismann is not found in Lake Zurich, nor in the small 

 lakes near Lake Constance. 



The above paper suggests several points well worthy the attention 

 of our local naturalists during the present and ensuing months. The 

 occurrence of the Nauplius form is of extreme interest, as an isolated 

 instance among Cladocera ; while the retention by the spring brood of 

 the Nauphus eye affords a ready means of recognising them in their 

 later stages. It will be very important to ascertain whether any of this 

 spring brood develope into males, i.e., whether any males are met 

 with possessing the Nauphus eye. Any direct confirmation of the 

 parthenoge etic nature of the summer ova would be also very valuable. 



A point which I would ask any one to determine who has the 

 opportunity of observing a living Leptodora, is the natm-e of the process 

 of respiration. This will probably be found to be effected, as in Cyclops 

 and other Entomostraca, by means of rhythmical contractions of the 

 terminal dilated portion of the alimentary canal ; water being alternately 

 sucked into and ejected from this dilated portion. The arrangement of 

 the muscular system strongly suggests that this is the real mode of 

 respiration, a point which would probably be settled by a few minutes' 

 obsei-vation of a healthy specimen. 



