2 



Gr. 0. SABS. 



[No. 8. 



tions, whereas at a later period, and more particularly when the 

 physical conditions of their habitat become less favourable, either 

 from the evaporatiou of the water or a considerable fall in the 

 temperature, true ova are finally produced, which have been fer- 

 tilized by the males, and, besides being furnished with a strong 

 egg-shellj in many cases become even enclosed within peculiar cap- 

 suliform envelopes, derived from the carapace of the parent indi- 

 vidual. These ova, generally called winter-eggs, are thus enabled 

 to retain their developing power even when completely dried up 

 during a long period, or exposed to the severe cold of winter, 

 as a rule not developing in our climate till the next spring. 



I could not but assume, that a similar mode of propagation 

 might also distinguish the fresh-water Entomostraca of Australia. 

 There, it is true, occurs no cold winter season, but, on the 

 other hand, a very marked and protracted period of drought, 

 during which most of the ponds and ditches, constituting the 

 habitat of numerous Entomostraca, dry up completely for a con- 

 siderable time, until they finally again become filled with water 

 during the heavy rain-fall that arrives at a later season of 

 the year. 



AccordiDg to the statements of Mr. Lumholtz, the mud 

 was tåken from a rather large lake, called Gracemere Lagoon, 

 situated at a distance of about 7 miles west of Rockhampton, in 

 North Queensland. This lake measures in length somewhat more 

 than a mile and in breadth half a mile, and has not anywhere 

 a considerable depth. In 1856 the whole lake was entirely 

 dried up, and continued so for the space of 9 months. During 

 the rainy season the lake is supplied with water from an adja- 

 cent rill, which seldom wholly evaporates. The mud was col- 

 lected at a depth of 5 and 10 feet beneath the surface of the 

 water, at the commencement of March (or end of February) 

 1882, and immediately dried before being packed and forwarded. 



On its arrival in Christiania, the mud resembled stone-like 

 masses, of a dark greyish colour, with a crust of a somewhat 

 lighter hue, and exhibiting numerous fissures and crevices coated 

 with a ferruginous deposit. It was very hard and compact, so 



