HENSEN, ON THE DECAPOD CRUSTACEANS. 31 
cells just mentioned, these are not permanent structures. 
They enjoy only a very short life. But the swarm-spores and 
the reproductive globules (Befruchtungskuglen), as soon as 
they have acquired a cellulose coat, become permanent cells 
(Daurezellen), from which a new individual is formed. The 
protoplasmic coat of the cells in question, assumes various 
degrees of thickness and density. 
On the Aupitory OrGaAN in the Decapop CRUSTACEANS. 
By Dr. V. Hensen. 
( Adsiract.)* 
Tue auditory organ of the Decapod Crustaceans is usually 
‘situated in the basal portion of the inner antenna, for it has 
been satisfactorily shown that the organ at one time termed 
an ‘‘auditory cylinder,” and enclosed in the basal joint of 
the outer antenna, has nothing to do with the function of 
audition, The true auditory organ was discovered by 
Rosenthal, in 1811, and in 1843 it formed the subject of 
careful studies by M. Favre. It has since been studied by 
several observers, and in particular by M. Kroyer ;+ but the 
details of its structure have nevertheless, in great part, re- 
mained a subject of dispute. The excellent researches of M. 
Hensen, which have extended to twenty-eight species of 
Crustacea, are therefore a welcome contribution on the 
subject. 
The auditory organ of the higher Crustacea is thus consti- 
tuted :—From the terminal ganglion of a nerve proceeds a 
delicate nervous filament, which enters a clhitinous hair, 
where it is attached to a part of the wall, presenting a special 
structure. The connection of this part of the wall with the 
rest of the clitinous skeleton is such as to allow of vibrations 
under the infiuence of sonorous undulations. Besides this, 
the extremity of the hair often penetrates between the 
otolites, or even into the interior of one. ‘The different parts 
of this apparatus must be considered a little more minutely. 
To commence with the otolites. MM. Leuckart and 
Kroyer have very properly described two types of auditory 
organs in the higher Crustacea, distinguished respectively by 
the open or closed condition of the orifice of the sac. In the 
* ‘Zeitsch. f. wissensch. Zool.,’ xiii, p. 819. Pl. 19—22. 
7 ‘Mem. de Acad. de Copenhague,’ 1859, t. iv, p. 287. 
