STYELOPSIS GROSSULARIA. 131 



Hab. Between tide-marks and in shallow water, on 

 the underside of stones ; on the roots and stems of 

 Laminaria, and occasionally on the fronds of fuel ; 

 common on oysters. [Adhering to the roots of 

 Laminaria (Fncus) digitata (Jameson). Commonly in- 

 vesting the larger marine plants, and on shells, stones, 

 etc. (Thompson}. ~\ 



Common on all our coasts. 



First record. Forbes and Hanley, 1848. [Jameson, 

 as Ascidia rustica, 1811.] 



[Styelopsis] grossularia (PI. XL VI, figs. 1-4) is an 

 extremely variable species, changing its appearance so 

 much in different situations and under different cir- 

 cumstances that we have sometimes been induced to 

 think that more than one species might be included in 

 it. When growing singly it is rather depressed, and 

 the test spreads into a thin membrane around the base 

 (PI. XL VI, figs. 3 and 4), but in sheltered situations, 

 as under shelving rocks, the individuals accumulate in 

 compact masses, so closely packed as to allow of 

 growth only upwards, and adhering very firmly to 

 each other at the sides (PI. XL VI, figs. 1 and 2). 

 The young in such cases often attach themselves to 

 the surface of the parent, so as at first sight to appear 

 as if budding from it (PI. XL VI, fig. 1). In the more 

 free state, likewise, the spreading bases of several 

 individuals sometimes come into contact and unite, but 

 on careful inspection the line of union can generally 

 l)e detected. The test, viewed as a transparent object 

 under a microscope, always shows transverse anas- 

 tomosing corrugations, but it often appears smooth to 

 the naked eye, especially in the young state. 



[Styelopsis] grossularia has been considered by 

 English authors to be the Ascidia rustica of Linnaeus. 

 Miiller appears to have been the first to mistake the 

 young of that species ; the description " Junior liemi- 

 spserica, mamillaris" in his ' Prodromus,' and the 

 smaller figures parasitical on the larger form in 



